Landing BF-109 is Easy ?

[Crump]

 

, it's unbelievable that we're saying one thing and you understand another, Crump.

 

 

I just understand what I was taught in aircraft design and what I learned adjusting landing gear as an aircraft mechanic.  If it is different from your experience, so be it.  I am sorry I have yet to find anything that warns "Only if your gear has camber......land it straight". 

[FuriousMeow]

I know with Jeeps, the real Jeeps (Wrangler), camber definitely has an impact on handling. Toe-in does as well, but if one wheel is differently cambered than the other then there is a significant(actually definite) potential for "death wobble" with the Jeep. It only occurs above a particular speed, which is around 55mph, and causes the front section to shake like the whole thing is about to rip off. It can happen when tires are improperly balanced as well, but when the tires show up to be balanced - taking a Wrangler to a tire shop will inevitably show either improper toe-in or off camber.

 

The death wobble is manageable with 4 wheels and only at 55 MPH, given that you slow down fairly quickly to prevent further linkage damage - but if something like that were to occur on a tri-pod, I'd imagine a quick dig in on one side leading to a less than stellar landing.

Edited December 3, 2013 by FuriousMeow

[Crump]

 

either improper toe-in or off cambe

 

Key word.  Of course anything improperly adjusted will not work as intended.

 

Properly adjusted landing gear will roll straight by design.  If that proper adjustment includes a large amount of camber....it will roll straight by design.

[JtD]

Properly adjusted landing gear will roll straight by design.  If that proper adjustment includes a large amount of camber....it will roll straight by design.

...for as long as the wheel load distribution does not get changed.

[Crump]

 

...for as long as the wheel load distribution does not get changed.          

 

Absolutely.  Which is why ALL conventional landing gear designs have to be set down straight on the runway.  Set any of them down with side load and the aircraft diverges.

 

Now we get it!! 

The stability is a function of the relationship of the main wheels to the CG not the geometry of the gear..

[DD_bongodriver]

Which was recognised to be significantly severely unstable in the 109, finally we have something to agree on.

[Sternjaeger]

guys, guys, guys, we're confusing things again. 

 

1) a bf109 tire, like most ww2 aircraft tires, has a semicircular profile, this is because you need a tire to perform its job at different angles of camber (if you come down on just one gear, the camber angle will be different, and will change until all three wheels are on the ground). Many tailwheels on the other hand have a square (or car-like, if you wish) profile, this is because they're meant to give the aircraft directional stability. This was something that was learned only later in the war though, and is a common sight on all US fighter aircraft. 

 

2) the peculiar behaviour of the 109 is not caused by the camber, but by the toe-out. The toe-out means that the wheels are not parallel to the longitudinal (roll) axis, but instead they slightly point outwards. In cars you have a slightly inwards toe-in to improve stability, whilst toe-out is used mainly to improve steering response. The 109 engineers gave the landing gear setup a slight toe out to help turning the aircraft on the ground and because of the peculiar landing gear position. It was the best design compromise they could come out with, considering the wing spar configuration and bearing in mind they wanted the landing gear joint to be on the main fuselage and not on the wing like on the Spitfire. 

 

So if you come down for landing and decide to put one wheel down only, the toe out will give a slight tendency to turn, which will then be counteracted by your contrasting controls. So now technically you are rolling on the wheel's longitudinal axis, which doesn't correspond to the directional one. The moment the other wheel comes down, the aircraft will then tend to straighten with another swinging motion, but if you don't compensate again the aircraft will keep on swinging, and with decreasing speeds your countering of the swing will have to be more decisive, as your control authority diminishes. 

[Crump]

 

the peculiar behaviour of the 109 is not caused by the camber, but by the toe-out.

 

Negative.  Gear geometry, camber, toe in or out makes no difference.

 

Properly adjusted landing gear will roll straight by design.

 

 

Which was recognised to be significantly severely unstable in the 109, finally we have something to agree on.

 

Semantics...severely unstable would be an improper design which is not the case.

 

Less directionally than some tail draggers is correct as well as being more longitudinally stable than some tail draggers.  The longitudinal stability is what allows the pilot to deliver more braking power without causing a propeller strike for short, rough, field landings.  Something an experienced pilot would appreciate.

 

The less directional stability is what makes the Bf-109 less tolerant of side load and easier to ground loop if mishandled by an inexperienced pilot.

 

It was not designed to teach fledgling pilots skills they should already have by the time they take the controls of state of the art fighter aircraft.

[Sternjaeger]

Negative.  Gear geometry, camber, toe in or out makes no difference.

 

Right, let's see if using an empirical experiment helps you understanding: take a treadmill, now take a wheel that you can hold by its rotational axis and hold it with a slight toe-out and camber angles related to the treadmill surface. 

 

When you put the wheel down on the treadmill, where will the wheel go? 

[DD_bongodriver]

Negative, camber, toe in/toe out will make massive differences, this is a simple theory to test, take 1 wheel til it on a camber either negative or positive and see for yourself that it WILL NOT track straight, same for toe in and toe out, effectively when applied to a single wheel it is basically steering.....by definition it WILL NOT track straight.

 

Severely unstable indicates a condition brought about by the compromised design of wanting to have the gear attached to the fuselage and splaying it out for wider track and not putting enough positive camber on the wheels so they can still fit into the wing on retraction.

Edited December 3, 2013 by DD_bongodriver

[Crump]

Right, let's see if using an empirical experiment helps you understanding: take a treadmill, now take a wheel that you can hold by its rotational axis and hold it with a slight toe-out and camber angles related to the treadmill surface. 

 

When you put the wheel down on the treadmill, where will the wheel go? 

 

 

Negative, camber, toe in/toe out will make massive differences, this is a simple theory to test, take 1 wheel til it on a camber either negative or positive and see for yourself that it WILL NOT track straight, same for toe in and toe out, effectively when applied to a single wheel it is basically steering.....by definition it WILL NOT track straight.

 

Severely unstable indicates a condition brought about by the compromised design of wanting to have the gear attached to the fuselage and splaying it out for wider track and not putting enough positive camber on the wheels so they can still fit into the wing on retraction.

 

 

Both assumptions that properly adjusted gear geometry makes any difference on a tail dragger is wrong according to landing gear design convention.

 

The aircraft will land straight as long as no side load is present and is a characteristic of any tail dragger.

 

In this photo, the aircraft touches down on one gear.  If there was some merit to these geometry theories contributing to the directional instability of the aircraft, our Bf-109 in this photo should ground loop.  It does not and lands normally.

 

Think about it, the most common approach technique in a high performance tail dragger, the curved slip to land to see over the nose would be impractical. 

 

 

 

http://www.youtube.com/watch?v=BzUUlO6ihwE

 

[Sternjaeger]

I'm starting to wonder whether you actually ever flown on a taildragger... the pilot is compensating like in the video here, check out the amount of aileron and rudder work

 

http://youtu.be/5nj77mJlzrc?t=1m4s

Edited December 3, 2013 by Sternjaeger

[DD_bongodriver]

our Bf-109 in this photo should ground loop. It does not and lands normally.

 

No, it should not do that if the pilot is actually compensating for it, and he certainly will be compensating hard due to it's instability.

 

[Gort]

Agree, toe settings are have a huge effect on handling. I think the adults here understand that, and I didn't know that the bf109 used toe out to enhance ground maneuvering. Very interesting indeed.

[Panzerlang]

Hands up anyone who thinks the BoS Digital Nature engine is able to take account of main-gear camber and toe-in/toe-out.

[DD_bongodriver]

Why not, my hand is up.

[SKG51_robtek]

Despite the semantic hardheads here i believe that the Bf109 is, and was easy to land by a pilot

who knows that one has to control the plane until it stands and not let the plane control itself by negleting necessary corrections.

[DD_bongodriver]

Test pilots will tell you different.

[SKG51_robtek]

Test pilots are paid to see errors! :biggrin: :biggrin:

[Crump]

 

 

 

 

I'm starting to wonder whether you actually ever flown on a taildragger... the pilot is compensating like in the video here, check out the amount of aileron and rudder work

 

http://youtu.be/5nj77mJlzrc?t=1m4s

 

 

No, it should not do that if the pilot is actually compensating for it, and he certainly will be compensating hard due to it's instability.

 

 

 

Rudder input is normal in any tail dragger landing.  The CG is constantly trying to swap ends as it is inherently unstable because it is behind the main wheels.

 

 

 

As a result, tailwheel airplanes will more readily swap ends on the ground unless the pilot continuously intervenes with corrective rudder inputs.

 

http://cpaviation.com/tailwheel-training/

 

 

Stall Landing

Stall Landing Outline

• Make normal approach to runway.
• By short final, eliminate any drift by lowering the upwind wing and keep the airplane straight with opposite rudder as necessary
• Make a normal flare to level flight just inches off the runway
• Keep working the stick/yoke back so as to not let the airplane land and keep it a few inches off the runway
• Strive to get the stick/yoke all the way back to its stop
• Allow the airplane to stall just inches off the runway
• Keep the stick back!!!
• Keep looking straight down the runway and steer the airplane with the rudders
• DO NOT let your attention drop one instant from maintaining directional control
• Keep the ailerons turned into the wind as necessary
• Keep the stick ALL THE WAY back!

Three-Point Landing

Three-Point Landing Outline

• Make normal approach to runway.
• By short final, eliminate any drift by lowering the upwind wing and keep the airplane straight with opposite rudder as necessary
• Make a normal flare to level flight just inches off the runway
• Keep working the stick/yoke back so as to not let the airplane land and keep it a few inches off the runway
• Strive to attain the exact attitude at which all three wheels will touch at the same time.  This attitude will probably be a little shy of the full stall attitude.
• Try to hold that attitude with the wheels just inches off the runway until the airplane settles onto the runway.
• Once the airplane is solidly one the runway, get and keep the stick back!!!
• Keep looking straight down the runway and steer the airplane with the rudders
• DO NOT let your attention drop one instant from maintaining directional control
• Keep the ailerons turned into the wind as necessary
• Keep the stick ALL THE WAY back!

Wheel Landing Outline

• Make normal approach to runway with normal final approach power
• By short final, eliminate any drift by lowering the upwind wing and keep the airplane straight with opposite rudder as necessary
• Make a slight flare to near-level flight just inches off the runway, but keep the nose down a little
• Let the main wheels settle onto the runway - be patient.  Use the elevator control to achieve this
• Once the main wheels are one the runway, chop the power and stick it on with a little forward stick/yoke if necessary (often chopping power will be good enough)
• Keep looking straight down the runway and steer the airplane with the rudders
• Hold the tail up with more and more forward stick/yoke until it settles on its own
• DO NOT let your attention drop one instant from maintaining directional control
• Keep the ailerons turned into the wind as necessary
• Once the tail comes down, immediately bring the stick/yoke all the way back into your gut and keep it there
• Keep the stick ALL THE WAY back!

 

http://www.taildraggers.com/Documentation.aspx?page=Takeoff

 

Normal tail dragger landing control inputs.......

[DD_bongodriver]

and the 109 did not handle like any other taildragger, it required much more compensation due to it's severe directional instability..........simple.

[Sternjaeger]

Normal tail dragger landing control inputs.......

 

the Bf109 wasn't a normal tail dragger because its wheels toe-out meant a great deal of counteracting when not landed on 3 points. This is not your microlight or a Piper Cub, capisc'?

[DD_bongodriver]

Test pilots are paid to see errors! :biggrin: :biggrin:

precisely, they are trained specifically to understand the processes that are causing those errors too, they are trained to give accurate feedback on the events, it becomes nature to them even when they get to fly aircraft that they aren't being paid to fly for the purposes of prototype development, when a test pilot remarks on the complexity of handling an aircraft it means it is complex to handle.

 

So I will continue to regard the opinion of test pilots above any other.

[Crump]

 

 they are trained to give accurate feedback on the events

 

 

Is not determining the cause of those events......

and the 109 did not handle like any other taildragger, it required much more compensation due to it's severe directional instability..........simple.

 

 

Semantics...severely unstable would be an improper design which is not the case.

 

Less directionally than some tail draggers is correct as well as being more longitudinally stable than some tail draggers.  The longitudinal stability is what allows the pilot to deliver more braking power without causing a propeller strike for short, rough, field landings.  Something an experienced pilot would appreciate.

 

The less directional stability is what makes the Bf-109 less tolerant of side load and easier to ground loop if mishandled by an inexperienced pilot.

 

It was not designed to teach fledgling pilots skills they should already have by the time they take the controls of state of the art fighter aircraft.

[DD_bongodriver]

Semantics...severely unstable would be an improper design which is not the case

 

but it was severly unstable, the design was a compromise........dare I say it, it really was improper, ideally it would have been a wide track without camber, that would be a proper design.

It was not designed to teach fledgling pilots skills they should already have by the time they take the controls of state of the art fighter aircraft.

 

Completely irrelevant statement, no front line fighter was designed for that purpose, yet most did not have the same instability.

 

The longitudinal stability is what allows the pilot to deliver more braking power without causing a propeller strike for short, rough, field landings. Something an experienced pilot would appreciate.

 

interesting part about this statement is that it requires the CoG to move aft to improve the situation, but in the air the same condition would have adverse effects on stability.

Edited December 3, 2013 by DD_bongodriver

[Crump]

Here is a Cessna 170 landing.  You can see the constant rudder input from the moment of touchdown which is normal operations for a tail dragger. 

 

http://www.youtube.com/watch?v=OXyVW2UMCK8

 

Another one, Landing a Champ, one of the most docile tail draggers in existence.  Notice the young pilot works the rudders constantly as is proper technique in a tail dragger.

 

http://www.youtube.com/watch?v=Id4dVzdeqYo

[DD_bongodriver]

Cessna 170 and Airnocker Chimps are not 109's

[Sternjaeger]

Here is a Cessna 170 landing.  You can see the constant rudder input from the moment of touchdown which is normal operations for a tail dragger. 

 

Edited December 3, 2013 by Sternjaeger

[Crump]

There have been a few posts about toe-in and toe-out on aircraft without really explaining the geometry of the spring type landing gear design. This does not apply to oleo strut, trailing link or bogie truck type gears.

 

 

With no weight on the wheels, a spring type gear has positive camber by design. This means the top of the tire centerline is tilted outward. Negative camber means the top of the tire is tilted inward.

 

As the aircraft enters a flare the pitch increases. With a pitch increase, the positive camber factors into two components, part positive camber and part toe-in. When the weight of the aircraft settles on the gear, the gear spreads. The spreading changes the positive camber into negative camber. This transition is more pronounced at higher weights. As long as the aircraft attitude is nose up with weight on wheels, the now negative camber factors into two components… part negative camber and part toe-out.

 

This transition from positive camber to negative camber, and toe-in to toe-out occurs on both conventional gear and tricycle gear.

 

If the aircraft has conventional gear, and negative camber with weight on main wheels and tailwheel, it will always have toe-out in the three point attitude.

 

However, if the aircraft is tricycle, the nose lowers after touchdown. This causes the toe-out effect of negative camber to transition back to near neutral toe-in while maintaining negative camber. ( There is a slight decrease in negative camber when some of the weight shifts to the nose gear.)

 

For tricycle gear aircraft, toe-in is stabilizing. As the aircraft turns, it leans against the outside tire. Because the CG is ahead of the tire the toe-in counteracts the turn much like a vertical stabilizer. Most tricycle gear aircraft are set up with slight toe-in with weight on all three gear.

 

For conventional gear aircraft, toe-in is unstable. As the aircraft turns it leans against the outside tire which is pointed into the turn. Because the CG is behind the landing gear the aircraft turns sharper and over-steers

 

Toe-out on a conventional gear is stabilizing. As the aircraft turns it leans against the outside tire which is pointing away from the turn. The tire angle decreases the turning tendency and directional stability is easily maintained by the pilot. . Most conventional gear aircraft are set up with slight negative camber with weight on wheels which results in a small toe-out component.

 

For an example of conventional gear toe-out stability one can look at aircraft equipped with “crosswind” landing gear. If too much pressure was put on the outside tire, the entire wheel simply casters to an extreme toe-out condition and removes any turning tendency.

 

 

If your aircraft is a bit squirrelly on landing, you might check the camber and toe angles with the aircraft loaded to the normal operating weight. If the gear is too stiff or bungees are too tight the gear may not be settling into the preferred negative camber position.

 

 

In summary, tricycle gear --- neutral or slight toe-in is best. Convention gear --- neutral to slightly toe-out is best.

 

I hope this clarifies the differences between conventional and tricycle landing gears and how they react with camber, toe-in and toe-out.

 

 

 

http://www.teamkitfox.com/Forums/showthread.php?p=10287

 

The toe out on the Bf-109 is designed to offer stability not instability. 

[Karost]

From "The Great Book of WW2 Airplanes" page 470,

=========================================

some direct quotes from Herbert Kaiser, a LW pilot with 68 credited aerial kills.

He indicates the BF109 was a very difficult airplane to fly, particularly for inexperienced pilots and particularly in landings and takeoffs because of the torque, narrow landing gear and poor ground visibility. No specific figures however. It does sound as if there must have been numerous landing and takeoff accidents which might have contributed to the "myth". The fact is that practically all WW2 fighters, especially the tail draggers, could be a handfull in landings and takeoffs. Many of the P40s the AVG received were wrecked in landing accidents before they ever saw combat. Tex Hill confirmed this in an interview.

 

 

"The JG26 War Diary: Volume 2 1943-5", P.290
======================================
"12th October 1940: I had hoped for a posting to an operational unit this month. Unfortunately, training is far behind schedule because of the bad autumn weather.

We have a rough time in training here also. There have been one or two fatal accidents every week for the past six week in our Course alone. Today Sergeant Schmidt crashed and was killed. He was one of our section of five.

We have spent several days on theoretical conversion training before flying the Messerschmitt 109, which is difficult to handle and dangerous at first. We can now go through every movement in our sleep.

This morning we brought out the first 109 and were ready to fly. Sergeant Schmidt was chosen as the first of us, by drawing lots. He took off without difficulty, which was something, as the aircraft will only too readily crash on take-off if one is not careful. A premature attempt to climb will cause it to whip over into a spin, swiftly and surely. I have seen that happen hundreds of times and it frequently means the death of the pilot.

Schmidt came in to land after making one circuit; but he misjudged the speed, which was higher than that to which he was accustomed, and so he overshot the runway. He came round again and the same thing happened. He began to worry; for Sergeant Schmidt had obviously lost his nerve. He was coming in and making a final turn before flattening out to touch down, when the aircraft suddenly stalled because of insufficient speed and spun out of control, crashing into the ground and exploding a few hundred feet short of the end of the runway. We all raced like madmen over to the scene of the crash. I was the first to arrive. Schmidt had been thrown clear and was lying several feet away from the flaming wreckage. He was screaming like an animal, covered in blood. I stooped down over the body of my comrade and saw that both legs were missing. I held his head. The scream were driving me insane. Blood poured over my hands. I have never felt so helpless in my life. The screaming finally stopped and became an even more terrible silence. Then Kuhl and the others arrived but by that time Schmidt was dead.

Major von Kornatzky ordered training to be resumed forthwith and less than an hour later the next 109 was brought out. This time it was my turn.

I went into the hangar and washed the blood off my hands. Then the mechanics tightened up my safety belt and I was taxiing off to the take-off point. My heart was madly thumping. Not even the deafening roar of the engine was loud enough to drown out of my ears the lingering screams of my comrade as he lay there dying like an animal. I was no sooner airborne than I noticed the stains on my flying-suit. They were great dark blood-stains and I was frightened. It was a horrible, paralysing fear. I could only be thankful there was no-one present to see how terrified I was.

I circled the field for several minutes and gradually recovered from the panic. At last I was sufficiently calm to come in for a landing. Everything was alright. I took off immediately and landed again. And a third time.

Tears were still in my eyes when I pushed open the canopy and removed my helmet. When I jumped down from the wing I found I could not control the shaking of my knees.

Suddenly I saw Kornatzky standing in front of me. Steely blue eyes seemed to be boring right through me.

"Were you frightened?"
"Yes, sir."
"Better get used to it if you hope to go on operations."
 

 

Reference : 

http://www.ww2aircraft.net/forum/aviation/bf-109-aka-me-109-landing-gear-myth-research-thread-29605.html

http://forum.il2sturmovik.com/topic/2359-bf-109-landing-gear/

 

PS. 

I found some thing "not" funny  when internet forum post about "109 landing gear" which end up in the same way

the first link  the poster was banned.

the second link the thread  was luck.

 

So please ...  not let it happen in this tread again.  

Edited December 3, 2013 by Karost

[Crump]

Sternjager says:

 

2) the peculiar behaviour of the 109 is not caused by the camber, but by the toe-out.

 

[Crump]

 

Many of the P40s the AVG received were wrecked in landing accidents before they ever saw combat.

 

 

Typical high performance tail draggers....

 

Same thing with the Spitfire and Hurricanes during the Battle of Britain.  Extremely high wastage rates just from the increase in operational tempo.  More flying = more landings = more landing accidents.

[Rama]

ok... enough. it's just the same arguments looping.

 

And for Crump and for your future polemics in future threads: no need to highlight your post with red color, bold unerlined characters and extra-large fonts. It doesn't give to your arguments any stronger meaning. The main result is for your posts to look agressive and polemistic. So if it's not your intention, better don't do it.

Also read forum rules #9, #11 and #16, and please try to understand the meaning and purposes of these rules. If you don't, I'll help you.