Fokker Dr.I

[greybeard_52]

First mission with Fokker Dr. I in the scripted campaign dedicated to it.
The aircraft is totally blocked in left turns. As soon as I tried it, I thought: << Here is another flight model ruined by the FIBS told by the pilots in their books! >>. I remember, in fact, the good old Panama Red who, in modeling the Nieuport 10, had multiplied the physical torque by four, because he had read in a book that it was "terrible", forcing the pilot to use all the pedal and all the stick. , at take off, to compensate for it!
But do you think a sane pilot would start not only to fly, but even to fight, with a plane that cannot turn left? And the state control bodies (in this case the Germanic ones - notoriously severe) would give the license for the operational use of such an uncontrollable device?
And, in any case, why, I wonder, alter the values of a known physical quantity, transforming a "physics-based" flight model into a "legend-based" one?
The parameters that come into play here are two: torque and precession. The first is simply: Torque = HP / RPM. The second would be equal to the ratio between the angular moments of inertia of the rotating parts and of the entire airplane, but it approximates perfectly as: Precession = Airscrew weight (+ engine for rotaries) / Total aircraft Weight.

[SYN_Vander]

It can turn to the left just as well, but use your rudder first. This is not about torque, but about adverse yaw.

[greybeard_52]

20 hours ago, SYN_Vander said:

This is not about torque, but about adverse yaw.

"Adverse yaw"!?? I took for granted that it was matter of (excessive) precession! Thanks for the tip!

[greybeard_52]

On 6/5/2022 at 12:56 PM, SYN_Vander said:

It can turn to the left just as well, but use your rudder first. This is not about torque, but about adverse yaw.

I have reviewed Dr. I's controllability taking into account your suggestion, and it always remains uncontrollable nonsense to me. As you are a tester, it is clear that you have to say that it is okay; it's like asking the butcher if the meat he is selling is good!
In fact, an aircraft has never been built where the adverse yaw effect is so high. I have seen the same error in some flight models for Red Baron 3D in the past, but when I myself put the actual physical parameters, the Fokker triplane only exhibited a slight tendency to pull up in left turns and plummet in turns to the right.

[1PL-Husar-1Esk]

Both adverse yaw and gyroscope precession take a big part in the coordinate Fokker turn. Most pilot dip the nose , then use rudder and ailerons to turn left. Other wise Fokker will pull up and yaw in opposite direction. 

[SYN_Vander]

2 hours ago, greybeard_52 said:

I have reviewed Dr. I's controllability taking into account your suggestion, and it always remains uncontrollable nonsense to me. As you are a tester, it is clear that you have to say that it is okay; it's like asking the butcher if the meat he is selling is good!
In fact, an aircraft has never been built where the adverse yaw effect is so high. I have seen the same error in some flight models for Red Baron 3D in the past, but when I myself put the actual physical parameters, the Fokker triplane only exhibited a slight tendency to pull up in left turns and plummet in turns to the right.

 

I didn't say it was okay, but that you can indeed turn left. We have a resident Fokker Dr1 owner on this forum, who you can ask if the behavior is correct: 

 

Edited June 7, 2022 by SYN_Vander

[Todt_Von_Oben]

Gents, adverse yaw is an effect; not a cause.

 

The term "adverse yaw" describes an undesirable yawing tendency which can be due to many things but is usually associated with asymmetric thrust in a multi-engine airplane. 

 

In the triplane's case, I believe the adverse yawing tendency in a left turn is the result of engine torque, gyroscopic precession, and P-factor.

 

I think those who've contributed to this thread have given good advice: one must be knowledgeable and bold with the rudder at the onset of the turn; leading with rudder and using your blip switch to reduce torque does work. 

 

Also, and as a general guideline: AMAP, keep your nose down (at least level and not much higher) in a left turn, if circumstances allow.  When they get you to follow in a climbing left turn, it's easy to stall-out.

 

Like most folks: for me, the triplane was a real challenge to learn to fly.  I had help, gave up twice, but always came back. 

 

She's not the fastest pony in the stable but in a knife-fight she's about as nimble as they get.  Without a vertical stabilizer, the ability to skid-shoot makes fine aiming adjustments possible at close range, too.   

 

The FC Camel and Dr1 are both great planes to fly and fight with; arguably the best aerobatic dogfight available in either sim.  They just take a little understanding and a bit of practice. 

 

So don't give up on either one. Learning to fly rotary-engine taildraggers in VR is one of the more satisfying experiences I've had in FC.

 

I hated 'em both at first; not anymore.  ?

 

Prosit! 

 

I'll add this: I believe this sim was developed by people who really understand Wolfgang Langewiesche.   I'm experienced with single and multi-engine taildraggers, and it still requires all my skill plus a joystick and rudder pedals to fly it right.  That said, it feels good; the planes are generally characteristic of what I'd expect.  So I'm thinking those who are having problems should first check their own skills and equipment before blaming the sim.  A non-pilot who mostly plays computer games and might be using a twist stick will probably have more difficulty learning to fly FC's rotaries than an experienced pilot might.

 

Edited June 7, 2022 by Todt_Von_Oben

[1PL-Husar-1Esk]

Adwerse yaw is present in many single engine propeller  driven aircraft with inline engines . In general we talk  about ailerons use and adwerse yaw, not about asymmetric thurst in duble engine aircrafts.  The rotary engine in Fokker adds quirks to it handling because it act like big gyroscope.  There are other forces acting on an airplane but those are not as pronounced as that two in The Fokker dr1.

Edited June 7, 2022 by 1PL-Husar-1Esk

[AndyJWest]

36 minutes ago, Todt_Von_Oben said:

Gents, adverse yaw is an effect; not a cause.

 

The term "adverse yaw" describes an undesirable yawing tendency which can be due to many things but is usually associated with asymmetric thrust in a multi-engine airplane. 

...

 

From NASA:

Quote

Yaw: Angular rotation about an airplane’s vertical (Z) axis. Yaw is produced by the rudder. Undesired yaw may also be produced by the use of ailerons or other roll controls for banking. This is called “adverse yaw” if the nose moves opposite the direction of roll and “proverse yaw” when the nose moves in the same direction. This undesired yaw is an example of coupling (motion about one axis causing motion about another axis) and is due to the lift vectors of the up-going and down-going wing being inclined at different angles during a roll. Therefore, a pilot of a conventional airplane must often use the rudder simultaneously with the ailerons to prevent
undesired yaw. This is often termed coordinating a turn.

https://www.nasa.gov/pdf/62553main_Exploring.the.Extreme.Guide.pdf

[Chill31]

On 6/5/2022 at 3:59 AM, greybeard_52 said:

First mission with Fokker Dr. I in the scripted campaign dedicated to it.
The aircraft is totally blocked in left turns. As soon as I tried it, I thought: << Here is another flight model ruined by the FIBS told by the pilots in their books! >>. I remember, in fact, the good old Panama Red who, in modeling the Nieuport 10, had multiplied the physical torque by four, because he had read in a book that it was "terrible", forcing the pilot to use all the pedal and all the stick. , at take off, to compensate for it!
But do you think a sane pilot would start not only to fly, but even to fight, with a plane that cannot turn left? And the state control bodies (in this case the Germanic ones - notoriously severe) would give the license for the operational use of such an uncontrollable device?
And, in any case, why, I wonder, alter the values of a known physical quantity, transforming a "physics-based" flight model into a "legend-based" one?
The parameters that come into play here are two: torque and precession. The first is simply: Torque = HP / RPM. The second would be equal to the ratio between the angular moments of inertia of the rotating parts and of the entire airplane, but it approximates perfectly as: Precession = Airscrew weight (+ engine for rotaries) / Total aircraft Weight.

The Dr.I in FC flies very much like the real plane upto the point of stall.  After it stalls, it is a wild departure from reality.  

 

To fly a left turn in a Dr.I, you must unload the wing to 1G, roll with plenty of left rudder, and then pull while maintaining almost full left rudder.  A climbing left turn in a Dr.I is a terrible idea, and impossible to maintain as airspeed decays.  

 

In this video, I did only pulled about 2Gs, so it was relatively easy to control, but notice the nose stops tracking, the engine quits, and it falls sideways for a moment.

 

 

My only amendment to that post is that my recent attempts to fly it on FC have resulted in me just spinning wildly in the sky from accelerated stall.  This is not representative of what I experience in the plane...maybe it is because I have lost some of my sim touch, but even when I haul the plane around the sky, it never departs wildly.

[greybeard_52]

44 minutes ago, Chill31 said:

The Dr.I in FC flies very much like the real plane upto the point of stall.

Hi Chill31 and thanks for your kind reply.

 

Just a question: is your Dr.I powered by a rotary or fixed radial?

 

Cheers

[=IRFC=Gascan]

I believe the very first post in the linked thread mentions the engines he has: both a 80hp Le Rhone rotary and a 120hp Le Rhone rotary.

[Chill31]

8 hours ago, greybeard_52 said:

Hi Chill31 and thanks for your kind reply.

 

Just a question: is your Dr.I powered by a rotary or fixed radial?

 

Cheers

I have flown it with 3 different engines.  O320 lycoming, 80 Rhone, and 120 Rhone (currently mounted).

[greybeard_52]

5 hours ago, Chill31 said:

120 Rhone (currently mounted)

Ok, so your Dr.I behaviour is higly representative of the historical one.

 

I think there's still some exaggeration in FC flight model (seemingly confirmed by your spinning from an accelerated stall), but the "core" point I believe is that the Fokker Dr.I became famous in my opinion only because the Red Baron found his fate in it. Actually, the venerable triplane was a nonsense from a design point of view: triplane formula is to improve visibility (shorter wing chord for a given total area and wingspan - and this was exactly the arrangement of the Sopwith Tripe), but Fokker chose a narrow wingspan, retaining wing chord. In addition, to worsen visibility, upper wing had the biggest chord and was without a "window" (like Camel) to alleviate. The Dr.I could still have an advantage from short wingspan about roll rate, but the choice of aileron only on upper wing denied also this possible strong point.

 

So why? I think Fokker was a good salesman, and he could have co-opted Manfred in some way (as depicted in the old movie The Red Baron, just about his triplane) as sort of "testimonial". The final result was that he sold some more aircraft, at cost of a little contribute to German defeat.

[Chill31]

10 hours ago, greybeard_52 said:

Ok, so your Dr.I behaviour is higly representative of the historical one.

 

I think there's still some exaggeration in FC flight model (seemingly confirmed by your spinning from an accelerated stall), but the "core" point I believe is that the Fokker Dr.I became famous in my opinion only because the Red Baron found his fate in it. Actually, the venerable triplane was a nonsense from a design point of view: triplane formula is to improve visibility (shorter wing chord for a given total area and wingspan - and this was exactly the arrangement of the Sopwith Tripe), but Fokker chose a narrow wingspan, retaining wing chord. In addition, to worsen visibility, upper wing had the biggest chord and was without a "window" (like Camel) to alleviate. The Dr.I could still have an advantage from short wingspan about roll rate, but the choice of aileron only on upper wing denied also this possible strong point.

 

So why? I think Fokker was a good salesman, and he could have co-opted Manfred in some way (as depicted in the old movie The Red Baron, just about his triplane) as sort of "testimonial". The final result was that he sold some more aircraft, at cost of a little contribute to German defeat.

 

I read in Fokker's autobiography that he went for a plane with maximum climb and maneuverability instead of speed.  I do think he understood there was a triplane craze, so he delivered that instead of a biplane.  He did talk about the Fokker V1, which was very good in his own eyes (he was a good pilot himself), but it was too modern for people to accept as it had no wing struts.  https://flyingmachines.ru/Site2/Crafts/Craft29781.htm  That plane was designed BEFORE the Dr.I.

 

I recently flew a Sopwith Camel (still working on the article and video), and despite having 4 ailerons, it rolls no better than the Dr.I.  In fact, the Dr.I is so much lighter on the aileron controls, I think it has an edge in roll reversals as you might find in a scissors type of dogfight.  

[greybeard_52]

1 hour ago, Chill31 said:

I recently flew a Sopwith Camel (still working on the article and video), and despite having 4 ailerons, it rolls no better than the Dr.I.

? Many years ago I did a study about WWI aircraft aileron efficiency, based on a NACA report (IIRC), detailing how aileron effectiveness was not only a matter of area, but it was also significantly influenced by wing plant, aileron shape and tapering, etc. Unfortunately I didn't keep the NACA report, but still have the results of my study, based on report formulas, applied to most of WWI aircraft, and Camel's ailerons result about 25% more effective than Dr.I ones. I don't want negate your experience, but can't deny as well numbers, physics and tests.

[Chill31]

8 hours ago, greybeard_52 said:

? Many years ago I did a study about WWI aircraft aileron efficiency, based on a NACA report (IIRC), detailing how aileron effectiveness was not only a matter of area, but it was also significantly influenced by wing plant, aileron shape and tapering, etc. Unfortunately I didn't keep the NACA report, but still have the results of my study, based on report formulas, applied to most of WWI aircraft, and Camel's ailerons result about 25% more effective than Dr.I ones. I don't want negate your experience, but can't deny as well numbers, physics and tests.

Interesting. I have videos of both aircraft performing rolls. They each take 6 seconds using full control deflection, but the Camel ailerons take 3 to 4 times the force on the control stick.  Based on your calculations, the Camel should be rolling in 4 seconds, but I was unable to achieve that (I did a lot of them bc it was fun!)

[greybeard_52]

1 hour ago, Chill31 said:

They each take 6 seconds using full control deflection, but the Camel ailerons take 3 to 4 times the force on the control stick.

I take note of your statement, and am curious to see the video. I would also like to know how the force on the control stick was measured (strain gauge?).

[Holtzauge]

@greybeard_52: The text citation below is an excerpt from a paper comparing the turn performance of the  Sopwith Camel and Fokker Dr.1 which can be found here:

 

http://www.theaerodrome.com/forum/showpost.php?p=751327&postcount=23

 

In summary, It looks like Mr. Carlson agrees with you: The gyroscopic forces on a Fokker Dr.1 are not that pronounced at all: 

 

"The author has had the good fortune to speak to the Swedish
aviator Mikael Carlson who has taken pains to build what is
arguably a carbon copy of a Fokker Dr.1 accurate down to
the last nuts and bolts. Not only that, but he flies it in
advanced manoeuvres as well meaning he is in a unique
position to talk about the Dr.1’s flying characteristics since
this is not a replica but an actual reincarnation of the plane
built and flown as it was in WW1.

Mr. Carlson’s Dr.1 is also authentic in terms of
instrumentation meaning there are no hard numbers on stall
and maximum speed available since he flies the plane as it
was flown back in WW1, i.e. by feel. Concerning turns, while
he has not timed them, he says there is no marked difference
in turn times left or right once settled into the turn but that the
gyroscopic forces do help in establishing a turn to the right
while opposing a turn to the left. He also confirmed that the
Dr.1 slows down rather quickly in tight turns, just as
predicted in the simulations.

Contrary to common belief, the gyroscopic effect in the Dr.1
is quite manageable and gyroscopic forces are in fact more

pronounced in a North American P-51 according to Mr.
Carlson who not only flies the Mustang but also the
Hangar10 operated Messerschmitt Bf 109G-6 putting him in
an authoritative position to judge these airplanes relative
handling characteristics. Interestingly, another airplane he has
flown that exhibits pronounced gyroscopic effects is not a
rotary powered plane but surprisingly enough the jet powered
de Havilland Vampire with its huge radial compressor.
Returning to the Dr.1’s gyroscopic precession characteristics,
he said these are quite manageable unless at very low speeds
close to stall and that consequently, he tends to lean a loop
slightly to one side in order to have control of in which
direction the Dr.1 departs should the speed become too low at
the top of a loop.

The Dr.1’s stall characteristics are very benign according to
Mr. Carlson and in fact the aircraft does not have a
pronounced stall point at all but kind of mushes when
exceeding the stall angle of attack while still retaining good
control authority which supports the popular legend that
Fokker’s thick winged Göttingen profiled Fokker Dr.1 and
D.VII had the ability to hang by the propeller to catch an
unwary Entente pilot from below.

In yaw the Dr.1 is neutral in directional stability meaning
that if the pilot uses rudder to give the plane a certain yaw
angle, it will stay there until the pilot actively uses the
rudder again to bring it back on track lending credence to
the Dr.1’s purported ability to fly sideways while firing its
guns.

When asked about the Dr.1’s spin characteristics, Mr.
Carlson said he has chosen not to explore this part of the
envelope since the high rotational speeds in a spin would
cause significant gyroscopic loads on the bearings of the
engine which seems like a prudent precaution given how
scarce and valuable the remaining original WW1-era rotary
engines are.

A further note of interest is that he said that the
aerodynamic overhang balances on the Dr.1’s control
surfaces work well and there is no tendency for
overbalance within the flight envelope and that the aileron
stick forces remain light allowing rolling manoeuvres even
at higher speeds which is in stark contrast to the
aerodynamically unbalanced ailerons on the Pfalz D.VIII24
which he says are hard to budge at higher speeds.

Another interesting point regarding the Dr.1’s aerodynamic
characteristics is that it is tail heavy and given Mr.
Carlson’s quest for historic accuracy, his Dr.1 has been
balanced as it flew in WW1 and the center of gravity is as
far back as 32 % MAC which explains the significant down
elevator needed on the Dr.1 to keep the nose down. In fact,
he has equipped his Dr.1 with a bungee cord connected to
the stick so that there is some level of trimming available to
handle the stick forces needed to maintain the pronounced
stick forward position needed to keep in level flight. With
the center of gravity so far back he points out, the aircraft is
basically unstable in pitch and needs to be flown preemptively
at all times.

Taxiing is best done with helpers on the wings assisting in
getting the aircraft in the right direction and lined up for
take-of. There is however directional control available
should it be needed, if the skid is unloaded and the engine
gunned to get sufficient airflow over the rudder. Landing
the Dr.1 should always be done as close to a three point
landing as possible and into the wind using the elevator to
push the tail down and get traction for the skid after
touchdown. Crosswinds are to be avoided as far as possible
and the plane is prone to ground looping and after
touchdown some engine power and constant attention with
the rudder is needed to maintain course. Attempting
wheeler landings is off the table as it is an open invitation
for a ground loop and consequently something he avoids
doing in the Dr.1.

As a final note on handling characteristics, Mr. Carlson
commented that pilots sometimes like to tell stories and
that the Dr.1 is in fact not that difficult to fly as long as you
have sufficient experience flying it. Different in the sense
that other combinations of control movement are needed
but as long as you are familiar with the airplane and the
somewhat unorthodox engine control, it is not that much
more difficult to handle than a more conventional plane.
That however said with the caveat that the Fokker Dr.1
does require the pilot to handle it in the correct way and
pay constant attention or, as he puts it, it will turn right
back and bite you."

[Chill31]

Mikael puts it very casually that it isn't difficult to fly.  Ask him how many people have flown his DR.I.  

 

I don't think he would say that gyro precession is not pronounced on the Dr.I.  You are using a LOT of rudder to compensate for gyro and maneuver the plane. I think he is a subtle guy and probably understated the impact of gyro forces.  Afterall, he is tilting the loop in order to preserve some level of authority over the plane...I'm guessing he isn't flying other planes that require such a concession.

 

Recently a rotary DrI crashed on take off, before even leaving the ground, due to pilot error in managing gyro forces... ?  pilot is fine.  Plane is a write-off. 

[greybeard_52]

9 hours ago, Holtzauge said:

The gyroscopic forces on a Fokker Dr.1 are not that pronounced at all

Thank you Holtzauge.

 

With all respect for pilots, as a graduate engineer can't understand why we must discuss respective opinions and experiences when a single number can give a definitive response.

As I already said in my first message, Precession = Airscrew weight (+ engine for rotaries) / Total aircraft Weight. This number is 0.28 for Dr.I and 0.29 for Camel.

[ZachariasX]

43 minutes ago, greybeard_52 said:

With all respect for pilots, as a graduate engineer can't understand why we must discuss respective opinions and experiences when a single number can give a definitive response.

Single numbers don't keep pilots from bending metal.

[Holtzauge]

About the gyroscopic forces being quite easy to estimate and quite manageable from an engineering perspective I agree completely: Being an aeronautical engineer myself I have done ballpark estimates of gyroscopic forces on my own and mathematically, control problems only occur at low dynamic pressures when the controls don’t have enough “bite”. In fact, the late Javier Arango, who was not only a pilot of good standing, also approached the subject from an engineering angle and even made measurements of how large the gyroscopic forces were on his Gnome powered Sopwith Camel in a video you can find here. I recommend watching this whole video though, which ties subjective pilot impressions together with a nice engineering analysis. IIRC then about 40% of the gyroscopic forces they measured came from the propeller, which certainly helps to put the contribution of the rotary engine into perspective. I think the misconception about a supposedly large contribution from the rotary engine comes from the notion that it’s a large spinning mass and therefore must give huge forces, when in fact the square of the distance comes into play which explains why propellers give such a large contribution even though they have a much lower mass than the engine. Finally, about the hint that I’m misrepresenting what Mikael has said about flying the Fokker Dr.1: I did the interview with him in two steps: First I interviewed him and then I wrote a draft. He reviewed it and what I posted above is text approved by him.

Edited June 13, 2022 by Holtzauge

[Varibraun]

8 hours ago, greybeard_52 said:

With all respect for pilots, as a graduate engineer can't understand why we must discuss respective opinions and experiences when a single number can give a definitive response.

 

7 hours ago, ZachariasX said:

Single numbers don't keep pilots from bending metal.

 

12 hours ago, Chill31 said:

Recently a rotary DrI crashed on take off, before even leaving the ground, due to pilot error in managing gyro forces... ?  pilot is fine.  Plane is a write-off. 

 

6 hours ago, Holtzauge said:

which ties subjective pilot impressions together with a nice engineering analysis.

 

Just letting all of you know that I am thoroughly enjoying this discussion as well as all the contributions from your deep expertise over the years.  I think Eric Brown and John Boyd would have too and would also agree with me that the 4 snips above is exactly why we have "Boffins" and Test Pilots in your field.

 

Regarding the DR1 flight model, as a non-engineer who spent a couple of years depending on the guy in the front of the OV-10 to keep me alive, I will still defer to Chris Hill (lifelong career pilot, USAFA, former USAF pilot, WWI replica pilot, owner/builder of fairly historically accurate DR1) at least until Mr. Carlson decides to start posting his flights and thoughts here in response to Chill.

 

Salute and Respect to you all!  Can't wait to see Chris' Camel video soon. 

[greybeard_52]

10 hours ago, Holtzauge said:

I recommend watching this whole video though, which ties subjective pilot impressions together with a nice engineering analysis.

Nice video; thanks for the link. I think a very interesting point is about WWI era pilot "slang"; e.g. "roll" meant as nowadays "snap roll". I believe this should be taken carefully in account when making a flight model on pilot tales basis (being understood that a pure physical model is the best, IMO).

[Holtzauge]

2 hours ago, greybeard_52 said:

Nice video; thanks for the link. I think a very interesting point is about WWI era pilot "slang"; e.g. "roll" meant as nowadays "snap roll". I believe this should be taken carefully in account when making a flight model on pilot tales basis (being understood that a pure physical model is the best, IMO).

 

Yes, it's a very good video and Mr. Arango's scientific approach to nailing down the Camel's flight characteristics is admirable. I also found that thing he said about pilot nomenclature now and then intriguing. Regarding the discussion here I think his 60% engine 40% propeller gyroscopic force measurement is key: If one makes a thought experiment and considers two aircraft we have in-game today, one with an in-line and one with a rotary, say the Albatros D.Va and Sopwith Camel, and remember how they are modeled in-game today with regards to gyroscopic forces and use this as a baseline. Then to get a ballpark comparison mentally double the perceived gyroscopic effects for the D.Va and halve them for the Camel, would the gyroscopic effects for these hybrid aircraft in-game be about the same? I don't think so. I think the modeling we see is just as you pointed out earlier, a result of customer expectations based on anecdotes read in pilot memoirs. I think one can draw a parallel here to the Me-109 elevator control force modeling in sims since the dawn of sims with Microsoft's CFS setting the benchmark early on with the Me-109 lawn darting in dives because it become uncontrollable already at quite low speeds. Why? Well because that is what pilot accounts and Eric Brown said! Those simmers that have been around a while remember that it took YEARS before this was fixed and the flight sims following CFS ported this modeling over because that was how the Me-109 "was" like to fly IRL according to the forum experts. Finally, here in this sim and DCS we now have a more controllable Me-109 but it took years before it was fixed and was like pulling teeth because it went against what "everyone" who had ever flown a sim, read a book or listened to a pilot account "knew"..........

 

Edited June 13, 2022 by Holtzauge

[Chill31]

Regarding gyro forces and their impact on the aircraft, I think the thing you are overlooking is the size of the aircraft control surfaces in relation to the gyro forces. 

 

I've flown some big iron T6 and T6II (T6II has a similar build to a P51 in terms of weight and dimension). Those planes do not require nearly as much control input to compensate for the gyro forces as the Dr.I.  I've never had a T6 (or any airplane for that matter) turn 90 degrees at the top of a loop.  

 

I have flown the Dr.I with a non-rotary and a rotary engine, so I am very familiar with the difference in handling quality. 

 

In FC, the control inputs I use are VERY similar to the inputs I use to fly my Dr.I.  

 

Where it departs reality is with high slip angles and post stall characteristics.  In FSX, high slip angles increase the stall speed dramatically, so I take that to mean it increases the AOA.  I think FC and ROF are built on very similar FM tech, and suffer the same problem in modeling high slip angles. My Dr.I will fly through very high slip angles with ease.

 

On top of it, the stall of the FC Dr.I is wild! The real Dr.I would would never break off into the wild spins we have in FC.  It is so gentle as to be arcadish in its recovery.

 

Same with the Camel, though the Camel has a more defined stall where the nose track stops and the wing drops at about triple the rate of the Dr.I.  (again, videos coming!)

 

I love Javiers contributions to WWI aviation history, but his tests with the Camel were done at such a benign level of maneuver that his results don't paint the full picture of the impact of gyro forces, ie his perception is that they are gentle and insignificant.  In my first left hand combat turn, the nose rose so sharply that I couldn't bring it back down with rudder!  I had to stop the pitch rate in order to yaw the nose back to the horizon.  

 

@HoltzaugeI don't think you are misrepresenting what he said.  I think Mikael is a very good pilot, and he is understating it when he talks to you about it.  In my conversations with him, we compare our experiences of flying the Dr.I through aggressive aerobatic maneuvers, and we both nod in agreement.  Yet Miakel has a way of saying things that make you think it is no big deal, when in fact, someone without his vast experience will face a monumental obstacle.  

 

On 6/12/2022 at 1:22 AM, greybeard_52 said:

I take note of your statement, and am curious to see the video. I would also like to know how the force on the control stick was measured (strain gauge?).

 

No, sadly, I didn't have a strain gage with me.  It is my estimation. It could be a lot more than that, but it is not less.  It felt like it must be 40 lbs of force?   

 

The Dr.I is so light on the controls that I would never consider two handing the control stick.  

 

The Camel...I switched to tossing it about with both hands for performing rolls with it.  Then I went back to one bc I didn't want to feel like a girl...

Edited June 13, 2022 by Chill31

[Varibraun]

6 hours ago, Holtzauge said:

I think the modeling we see is just as you pointed out earlier, a result of customer expectations based on anecdotes read in pilot memoirs.

 

6 hours ago, Holtzauge said:

was like pulling teeth because it went against what "everyone" who had ever flown a sim, read a book or listened to a pilot account "knew"..........

 

Agreed about memoirs and recollections, and that is what I enjoy about following your discussions in these threads with Chill, is that it isn't simmers reading Brown, or in this case, Richthofen, arguing accounts and resulting expectations vs. the in game FM.  Instead, here you have a very experienced pilot in THE aircraft testing and video recording the actual FM and then willing to engage in rationale discussion of the physics and formulas applied in the real world with the professional engineers as it specifically relates to our FC DR1 FM. 

 

Fascinating...at least to me, so thank you again for the time you spend here.

[greybeard_52]

3 hours ago, Varibraun said:

Instead, here you have a very experienced pilot in THE aircraft testing

I think Varibraun here hit an important point, that I too would enlight about my opinion expressed so far in this discussion: WWI pilots and test pilots are two different categories. While the former, as mentioned by Mr. Arango in the above linked video, where accustomed to drive horses, the latter are an invaluable compendium to help designer fixing, tuning and refining his work.

 

6 hours ago, Chill31 said:

No, sadly, I didn't have a strain gage with me.  It is my estimation. It could be a lot more than that, but it is not less.  It felt like it must be 40 lbs of force?

This is where a scientist collaboration is required. Numbers are objective, personal impressions may be influenced by alot of variables. Exaggerating, I recall the intervention in such a discussion of a police official who told that in an occasion he collected 21 testimonies of eyewitnesses of the same event and each of them narrated a story completely different from all the other ones... In your instance, the Camel could be badly rigged...

Edited June 14, 2022 by greybeard_52

[ZachariasX]

I think pilot accounts always have to be read with having "what was expected of an aircraft back then" in mind. Pilots will point out deviations from what they are used to. Mikael Carlson is used to just about any quirk a plane could exhibit and he has the incomparable ability to listen to the aircraft and then fly it according to how the aircraft is meant to be flown, wants to be flown. In this sense, I am not surprised by his judgement. If you can do that, only a plain unacceptable aircraft will be frowned upon. Yet many of those aircraft that exhibit "special tendencies" will undoubtably kill pilots that expect (and can handle) a Cessna-like behaviour.

 

Also, I do think one cannot take nominal values about stickforces at face value to assume, "if a can push that at the bench, then I'm good". If I placed any average GA pilot and sat him in an aircraft that starts with 40 lbs stick force, and tell him "now fly it and land that, alone", that person will unquestionably have a monumental scare, even if he/she is physically able to move the stick.

 

I must admit, the first moment when it was "my controls" in the Mustang, there was a slight scare when I noticed how solid the stick was and how much force even casual deflections took. It is by no means that hard, but you really have to get used to use a force that will easily break any desk monted flight stick. And it makes constant maneuvering a considerable workout. The stick wiggling in defensive BFM maneuvering we casually do in the game is just not in the cards.

 

I would compare plane controls (and their authority) like a kitchen, where each piece of furniture is placed in specific locations. While nominally, it may feature a dozen tea spoons, if they are by design placed in a top drawer, you might just get used to stirr the tea with the back of a fork from a conveniently placed drawer. Nominally, there is a spoon, but in practice, there is none. If your hot plate is placed too high, you might get used mainly using just the toaster. Depending on your needs, as always. You mainly using the toaster tells us more about you and the kitchen than the factual presence of a hot plate, same as you stirring tea with the handle side of a fork.

 

Udet was a short, but physically stong person. He was also used to any obscene tendencies a plane could have and was mainly ok with that. Everything about the 109 just reflects these requirements and non-requirements. As long as the plane was fast and he could roll and loop it, it was all fine. Hanna Reitsch was a tiny lady (especially for German standards) and she had a horrific time at the single controls of a Me-321 Gigant because she could hardly move the controls at all. When she complained, Willy told her to b*gger off as she was a weak woman anyway. To get dead pilots, you really don't need enemies to shoot you down when you have such designing engineers. The fact that later on, they used two pilots because of precisely that reason tells us a lot. Hans Peter, who was a Me-323 pilot, recounted that it took the full pull strenght of both pilots to make the Gigant take off the runway. What we see is casual use of a design that is by no means acceptable at all after todays standards. Good luck with someone placing the 88 gun one foot too far in front in the loading bay.

 

Everybody can make their own decison if the would fun loop a 109 at ground level that might well ask for all their strenght in the pull out. The point is not about being able to do it. The point is how much reserve do you want to have. (And can you do out twice? Three times? You still have the muscle? There's only one way to find out...) And that spoon is definitely in a top drawer. (It's not that you cannot get up there to fetch it...) The fact that none of the warbird pilots I spoke with would loop the 109 or the Buchon at air show heights (they usually roll it out of the loop) basically confirms to me that there is a practical limitation in control. While you can access it when you really must, it is venturing in dangerous grounds and you will avoid that should you care for your life or the aircraft. While it appears to me that those limitations certainly color Eric Browns assessment, Bob Hoover only had outward spite for describing the 109's handling qualities. Bob Hoover might have had a very peculiar way of flying aircraft and the 109 being obviously problematic for aileron rolls after take off etc., but it really shows me how narrow the scope it of what the aircraft can readily give you and how good you must be to make use of just these qualities in order to justify all the downsides.

 

Thus, I think the actual use of things tells as much as respective impressions about using them, as the latter is always in context of the former.

[Holtzauge]

Granted, my “hot ship” aerobatics piloting is limited to the Pitts S-2 and I have not yet flown a WW2 fighter although it’s on the bucket list. However, I do have extensive experience flying gliders both in competitions and as an instructor. But that has nothing to do with WW1 scouts and WW2 fighter you may say!?

 

Well yes and no: My point is this: Familiarity breeds confidence irrespective of aircraft class. As a first example, the best high performance glider we had at the time in the 1980’s (Yes I know I’m ancient, many of you were not even born then!) was the Std. Libelle. IMHO this aircraft handled very well, had light responsive control that required only small displacements and the force to move the controls were about the same on all axes. I flew this plane a lot and liked it.

 

I then entered a Club class competition and the best aircraft the glider club allowed me to use was the SF-27. Now this was a completely different beast: It had an all flying tail which made the stick forces in pitch very low over the complete speed range. It was also very twitchy in pitch. This was in stark contrast to roll: Speeding up between thermals, there was no other way to get it into a turn (when you felt you entered a thermal) other than slowing down a lot since at anything higher than turning speeds, the ailerons felt like they were set in concrete (Now where have we heard that description before…..). However, I was stuck with this bird for the competition and that was that. But as the week progressed something strange happened: I stopped whining, adapted and got on with the job and by the end of the competition, the SF-27 and I were quite bonded.

 

So what happened next? Well when I got back from the completion, I of course jumped right back into the Libelle as soon as I could. Taking off, I was horrified by the Libelle’s controls: It was far too sensitive in roll and the relationship between stick forces in roll and pitch felt unbalanced! I of course quickly came to my senses, since objectively, the Libelle is the better handling aircraft. But I still remember my initial impressions when I made the switch. In addition, had I spent 5 years flying the SF-27 as if my life depended on it, I would no doubt have taken even longer to accept the change.

 

A second point I want to make and which I believe is not just limited to glider pilots: Pilots on the whole are just like in any other walk of life very much individuals in their preferences and abilities. One thing that has always amused me working as an instructor is the stick style: This is a bit like you can tell who is sending Morse code on a radio by their “style”. The same is true for stick handling: I have flown with many pupils from greenhorns to military and professional pilots and some will keep the stick rock steady, other flip it about incessantly. Going with another glider example: In our club we have a Duo Discus and  a DG-1000 and the club is split down the middle which handles the best. I prefer the Duo since it’s more agile in roll while the DG has much higher aileron control forces. But others in the club like the DG  because it's “so steady” in turns once established. So which half of our club is right? You tell me……

 

And yet again the Me-109 is pulled forward as being problematical in pitch: My answer to this is partly based on the SF-27 story and familiarity: Which you prefer will be dependent if you are used to flying a Spitfire or a 109: Your motor control functions, stamina and strength will adapt to what you have and familiarity breeds confidence. In addition, why do most 109-complaints come from Allied pilots? I don’t recall seeing that many Germans complain about the Me-109 elevator control forces? And then you have the Finns: You can find a lot of Finns who were very happy with the Gustav!

 

Last but not least: The Me-109 flew from the war's beginning to the very end and IF this REALLY would have been a big problem the Germans would have fixed it because doing that for an elevator control system is not rocket science (e.g. tweak the balancing or add a Flettner tab etc.). But the Me-109 was produced in +30000 units and was the backbone of the Luftwaffe and it never happened? I wonder why? Well maybe, just maybe, because the pilots who flew them on a daily basis and were familiar with them did not think it was a problem……..

 

I rest my case.

 

 

Edited June 14, 2022 by Holtzauge

[Chill31]

@greybeard_52 I think Holtzeug is right, once you get used to the Dr.I, you will think nothing of it.  In FC, it is quite flyable through left turns. Just remember climbing left turns are not your friend, just as in the real plane.

 

For sure, rigging up a WWI plane with all sorts of testing equipment would be nice. Im just not quite there with having all of the equipment (on my way though!)  The Camel stick force changes with airspeed. At slower speeds, say after a tight turn, the stick force is probably half of what it is at speed (90 mph+).  The rigging on this plane could be in error. As it is the only one I've flown, I cannot know for certain. However, other aircraft of the time with similar wing/aileron configuration have the same heaviness in the ailerons (N28, Pfalz D8, Bristol F2b), so I think the Camel is probably not far off, if it is off at all.

 

FWIW, I feel like I am flying a Dr.I in FC, all the way up to the point it stalls or I make a big rudder turn.

 

 

[Holtzauge]

@Chill31: I hope I don’t come across as too contrarian: I think arguing different perspectives constructively brings things forward and I hope you agree. I think I can speak for many here that we do appreciate your input: The info and videos you provide about the Fokker Dr.1 are invaluable to understand more about these aircraft not only from a piloting, but also from an engineering perspective. So thanks for that and your very useful YouTube videos! That being said, I want to remind you of your promise to deliver Levil BOM data for the Dr.1: Was it like 6 months ago you said “next weekend”? 

 

How’s that going? I know you said something about induction leaks? Would be great to see some climb and speed data with your new 120 hp Le Rhone mounted. I mean, I know there are a lot of people here hoping to see a higher top speed than we currently see in-game today, but even if this does not pan out, to get actual bona fide data on such a close replica such as yours would be just great!

[greybeard_52]

Tolstoy used to say that it is impossible to change people's minds with words. Maybe he was exaggerating, but I can't help but conclude that since the tendency to climb in left turns is a consequence of precession, and the physics says that Dr. I's is pretty much the same as that of the Camel, I can't see because this effect is so pronounced in the Fokker triplane, as well as modeled in FC.
However, you all know that I enjoyed the conversation very much and I learned something from all your experiences (e.g. from the video of Chill31 I learned how to manage the landing without ALWAYS ending in a ground loop!)?.

[Cynic_Al]

On 6/5/2022 at 8:59 AM, greybeard_52 said:

Torque = HP / RPM.

 

This would seem to suggest that a stopped engine would generate infinite torque.

 

 

On 6/5/2022 at 8:59 AM, greybeard_52 said:

Precession = Airscrew weight (+ engine for rotaries) / Total aircraft Weight.

 

A given engine will generate the same precession regardless of the body to which it is mounted.

 

The term weight is for shopkeepers, you should use 'mass', but perhaps you just shouldn't.

 

 

4 hours ago, greybeard_52 said:

I can't help but conclude that since the tendency to climb in left turns is a consequence of precession,

 

It is not.  The reaction that causes a pitch-up movement when the aircraft yaws to the left, is caused by Gyroscopic Inertia; this effect is present only when the orientation of the rotating engine changes, whereas Gyroscopic Precession is present whenever the engine is rotating.

 

[ST_Catchov]

Not once does anybody mention the size and placement of the balls required to fly these rotary contraptions with balance and confidence. It should be a mandatory inclusion in any mathematical precession formula.

[Chill31]

@HoltzaugeI had 2 planes go down for maintenance at the same time, so I ended up fixing them for a few months and now I'm try to fix some aesthetician details on my Dr.I since it will be sitting next to the 3 nicest Dr.Is in the world at the Fokker Scourge...no pressure right?

 

I did go through the induction tubes, and I think everything is sealed. I did one demo flight after I fixed them, BUT I only had 40 minutes fuel...so no time for testing.  She is just waiting on her face-lift before returning to flight.  On the brightside, I should get to race my Dr.I against Mikael Carlsons as well as mount the BOM on his Dr.I and Old Rhinebecks Pup.

 

@greybeard_52 I am with you on the Camel behavior vs Dr.I, but I think it is the Camel that has the FM problem, not the Dr.I.  We read all about Voss' flat turn, but guess what, the Camel does it too!  The stability of the Camel shares many traits with the Dr.I, only slightly more stable in yaw and roll.  

 

Truth be told, all of the short rotary planes with fuselage lengths that are the same as the Dr.I should have real trouble turning left.  

[Holtzauge]

@Chill31: Well when it comes to paint scheme, I think you hands down have the coolest “skin” on your Dr.1 so you have that covered NP. Racing Mikael to see who is top dog on speed is all well and good but please remember all us number nerds who want a number! If you can get Levil BOM data on yours and Mikael’s Dr.1 (and anything else!) that would be smashing!

 

@ST_Catchov: While size certainly is important, also ensure that they hang low: The moment of inertia goes up with the square of the distance so always wear roomy boxers. This also ensures that you can hear the brass jingle.

[ST_Catchov]

42 minutes ago, Holtzauge said:

While size certainly is important, also ensure that they hang low: The moment of inertia goes up with the square of the distance so always wear roomy boxers. This also ensures that you can hear the brass jingle.

 

Precisely Holtzauge. As I intimated it's all about placement .... to balance (if it's done right) the gyroscopic forces. Heating, of course, was always problematic hence your reference to brass. It is a pertinent point.

 

That aside, this thread is a most interesting topic especially the input from chaps who fly these wonderful old kites in versions as close to the originals as possible.

 

4 hours ago, Chill31 said:

but I think it is the Camel that has the FM problem,

 

This is worthy of further discussion. I also hope I'm still vertical when Chill gets his Se5a flying. 

 

 

[Zooropa_Fly]

36 minutes ago, ST_Catchov said:

This is worthy of further discussion. I also hope I'm still vertical when Chill gets his Se5a flying. 

 

Highly unlikely due to the time differential.

 

 

 

1 hour ago, Holtzauge said:

The moment of inertia goes up with the square of the distance so always wear roomy boxers.

 

So all these years, wearing tight pants has disadvantaged me ?

Back to ST protocol then.. socks only.