Yak-1 flaps down arcadish behaviour?

[Maxyman]

I agree, this is a good illustration of the working principle. But if you were referring to this calculation when you said something about 5-6° at 700 IAS, I'd say this is far outside purpose of that estimate.

About friction, you'd need data to estimate it, down to the precision of the bearings, lubricant, stiffness of material, accuracy of assembly and so on. Imho, impossible to predict reasonably accurate from theoretical data.

You can't neglect friction under any circumstances. Even well maintained control surfaces required pilot inputs of several N to be moved at all, in most aircraft for most controls, it were several dozen N. You can expect no less from a flaps system design to operate under forces of several thousand N. And it's going to get worse when several thousand N are indeed applied.

Totally agree. Who is going to calculate (or extrapolate test data) the friction to verify the existing model?

 

Again, the reference I provided was a bug report to prove that the initial model was incorrect. I'm not saying that friction is not modeled now.

[JtD]

Back home, at my sources. Find attached chart about loss of maximum speed for mm opening of flaps. 50mm correspond to small opening of about 7° and cost 25 km/h.

 

Flaps were supposed to be successfully deployed on the ground at 3-5 kg/cm² pneumatic pressure, that can be taken as an estimate of friction in the system.

[TWC_Ace]

90% of VVS flyers in MP flies in Yak fighter "flapsing" and doing circles around messers...

 

its ridiculous really because we have an "elephant in the room"

Edited August 23, 2015 by blackram_

[Maxyman]

Back home, at my sources. Find attached chart about loss of maximum speed for mm opening of flaps. 50mm correspond to small opening of about 7° and cost 25 km/h.Flaps were supposed to be successfully deployed on the ground at 3-5 kg/cm² pneumatic pressure, that can be taken as an estimate of friction in the system.

Now we are talking. Can you please PM the full document?

[NachtJaeger110]

Just to post some more Yak1 specific technical data that might be of interest..

 

If anyone can read russian, I found this on avialogs.com.

Besides, there are many drawings in it. As far as I could see It is not the source of the flap drawing posted in the russian forum.

 

http://www.avialogs.com/index.php/en/aircraft/ussr/yakovlev/yak-1/yak-1-plane-technical-description-part-2.html

 

I think the flaps are discussed on pages 18 - 20 if I recognized the drawings correctly.

Edited August 24, 2015 by NachtJaeger110

[bivalov]

Now we are talking. Can you please PM the full document?

похоже что это из Степанца "Как летать на Яке" (1945), из того раздела, где описывается влияние отсоса щитков на скорость.

 

Дуплет как раз упоминает их в своих выводах.

 

As far as I could see It is not the source of the flap drawing posted in the russian forum.

there were used technical description of Yak-9, personal calculations/tests of Dooplet11, and exactly this technical description of Yak-1 M-105PA (spring'42).

Edited August 25, 2015 by bivalov

[Sokol1]

 

http://www.avialogs.com/index.php/en/aircraft/ussr/yakovlev/yak-1/yak-1-plane-technical-description-part-2.html

 

I think the flaps are discussed on pages 18 - 20 if I recognized the drawings correctly.

 

Pages 18-20 is only about flaps construction.

 

The mechanism is in page 56. Picture 90 is the "Flaps control piston cylinder" (риc.90 Поршенв цилиндра управления щитками).

 

uploading pictures

 

In page 57 are something about "full speed" and  "50º".

[NachtJaeger110]

 

 

In page 57 are something about "full speed" and  "50º".

 

Hm I typed it in with a russian keyboard app and gave it to Google translate:

 

"при движении штока цилиндра на полный ход щитки отклоняются на 50°"

 

"when moving the cylinder rod at full speed flaps deflected 50 °"

 

 

But we have to be careful with the context here of course, I'm not sure what "full speed" refers to

 

Edited August 25, 2015 by NachtJaeger110

[JtD]

"Full travel", not "full speed".

 

Anyway, does anyone know the exact details of the flaps mechanism, including arm lengths, cylinder travel or cylinder diameter? It looks to me as if everything posted in the 'calculation' (more accurately 'system explanation') in the Russian forum were just assumptions.

 

Also, the Yak-3 manual states in case of an aborted landing, don't retract flaps below 100m and 260km/h, because you'll lose about 50m of altitude. In order to avoid that sudden loss of altitude, you may move the flaps lever into the neutral position instead of into the up position, and flaps will retract gradually.

[Tektolnes]

Are the flaps on the Yak-1 and Yak-3 the same? The manual version I saw indicated it was for the Yak-1, Yak-3 and Yak-9 and it described that section JtD posted above.

[JtD]

There were small changes in the flaps systems as time progressed, but overall the flaps system on an early Yak-1 and a late Yak-3 or even 9u are very similar. The same section I posted for the Yak-3 is also in the Yak-1 manual, but gives 250km/h as the low speed limit.

[Tektolnes]

There was a UK company that did a restoration job on a Yak-1 not too long ago. They even used a genuine Klimov engine as opposed to the normal Allison for restorations. As part of that job they sourced a huge amount of technical data from the Yak Design Bureau. I'll send them on an email tomorrow to see if they'd be willing to shed some light on the subject.

[NachtJaeger110]

Great idea Tektolnes, much appreciated!

 

Do you mean this one?

 

http://hawkerrestorations.co.uk/restoration/yakovlev-yak-1/

 

(more, older pictures from this restoration:)

http://hawkerrestorations.co.uk/_images/_completed/yak1/yak1wing.html

Edited August 25, 2015 by NachtJaeger110

[TWC_Ace]

For the sake of "I experinced myself" I tried last Yak last night in MP in Wings of Liberty (great server btw) and oh boy...I could turn all day like maniac with flaps down even at higher speed. Didnt bleed much of an energy. Got 2 kills and Im a bad bad pilot.

 

well thats it

[Dakpilot]

The point you are missing is that when you say "didn't bleed much energy even at high speed " why should it? (bleed energy) they (flaps) have retracted, I am sure you can turn all day like a maniac in an F4 with flaps at 10-15 degrees

 

Cheers Dakpilot

[Tektolnes]

Do you mean this one?

 

Yep that's the one although it's gone to Retrotec since to get done. They're looking to sell it for £3m which would cover the cost to get it finished.

 

http://www.yak-1.co.uk/

[Maxyman]

Back home, at my sources. Find attached chart about loss of maximum speed for mm opening of flaps. 50mm correspond to small opening of about 7° and cost 25 km/h.

 

Flaps were supposed to be successfully deployed on the ground at 3-5 kg/cm² pneumatic pressure, that can be taken as an estimate of friction in the system.

Maximum speed without flaps in the quick mission at the altitude = 300m is 545kmh. Maximum speed with flaps = 391kmh. The flaps angle = 21°. The loss of speed is 154kmh.

 

Let’s assume your chart is a parabola y=ax²+bx+c, where x – flaps opening (mm), y – loss of speed (kmh). Three points from the chart: (x₁, y₁), (x₂, y₂), (x₃, y₃) are (60, 30), (70, 37), (80, 45).

The rough formula is y=x²/200+x/20+9.

 

The calculated loss of speed for the angle 21°(or 160mm) is 145kmh.

The energy loss looks reasonable to me.

Edited August 26, 2015 by Maxyman

[JtD]

I agree. As can be seen from my calculation many weeks ago, I don't think that parasitic drag increase for flaps down for the Yak is very wrong. The Fw190 should imho be checked.

[NachtJaeger110]

ok that's very convincing!

Together with the Spitfire and Wildcat Data I think you busted that part of the myth.

 

This leaves the question for the flaps structural strength.

[6./ZG26_5tuka]

There's more aerodynamical characteristics of flaps aside from drag. AoA behaviour is a way more important issue that still has not be prven corrcet (likewise why it's so much superiour to other fighter's flaps inagme).

 

Also stall speed at higher AoA may be off. See what I wrote about climbing with extendet flaps.

[Tektolnes]

I think there's two open questions:

 

1. Do the flaps being lowered give results similar to the Spitfire & Wildcat data i.e. they're really only beneficial in certain limited flight envelopes? I guess this is something that we can test.

 

2. What happens if the flaps were put in the neutral position at high speed? BOS doesn't really simulate this as far as I can see. BOS just has flaps up or down whereas the Yak-1 has up, neutral and down. I think Bert Foster's contact answered what would happen if you tried to force them down at high speed - they'd likely detach themselves. But if put in neutral to let the airflow control them it's not clear what would happen? It doesn't seem to be clear in any manuals what airspeed would cause flaps in the neutral position to end up fully retracted and locked (or if that even occurs in the neutral position).

[NachtJaeger110]

Ok, what methods do you suggest to test these three issues as accurately as possible?

 

(e.g. only possible with more historical data, asking experts from the restoration, ingame test? Tryin' to keep this accessible )

Edited August 26, 2015 by NachtJaeger110

[Maxyman]

2. What happens if the flaps were put in the neutral position at high speed? BOS doesn't really simulate this as far as I can see. BOS just has flaps up or down whereas the Yak-1 has up, neutral and down. I think Bert Foster's contact answered what would happen if you tried to force them down at high speed - they'd likely detach themselves. But if put in neutral to let the airflow control them it's not clear what would happen? It doesn't seem to be clear in any manuals what airspeed would cause flaps in the neutral position to end up fully retracted and locked (or if that even occurs in the neutral position).

Nothing happens. The flaps remove themselves completely at 250kmh in neutral position let alone higher speed.

 

The only interesting factor to consider is mechanical friction in the system, as JtD suggested.

[Tektolnes]

Nothing happens. The flaps remove themselves completely at 250kmh in neutral position let alone higher speed.

That would be the down position? The neutral position is what we have in BOS where the airflow dictates the degree to which the flaps are down once we start going over 250km/h. Right now we can select the neutral position at any speed in BOS without any possibility of damage. I'm not too technically inclined - is this what looking at the mechanical friction is supposed to check?

[Bert_Foster]

How do you select the neutral position at the moment in BOS ?

 

Which then brings the question how was it supposedly used in combat ? I mean Yak1 pilot is approaching the merge lets say at 450Kmh IAS. He wants to select "Combat flaps" .... how does he physically do it ? .... As I understand it as he approaches the merge the flap lever would be in the neutral position with the flaps physically retracted .... what next ?

[Maxyman]

The neutral position is what we have in BOS where the airflow dictates the degree to which the flaps are down once we start going over 250km/h.

That only can happen if the lever is in the "down"(or release flaps) position.

[Tektolnes]

Flaps down in BOS is the equivalent of the neutral position in a real Yak. The flaps down position in the Yak doesn't seem to be coded into BOS.

 

As I understand it in combat the pilot would have the lever in the up position and could get combat flaps by dropping it into the neutral position. They'd be kind of weird though as they wouldn't be a standard degree - they'd be constantly changing as your speed changes. The more they slow you down or the more a turn slows you down the lower the flaps would go. Probably pretty tricky to manage from an ergonomic perspective IRL but simpler for us in the game which is probably why lots of people use them all the time.

 

Edit.. can see above that my understanding seems to be wrong so ignore probably!

Edited August 26, 2015 by Tektolnes

[JtD]

What I understand about the flaps:

 

Assume they are in the up position, properly locked, flaps control lever in neutral: Both chambers of the actuation cylinder are empty, the flaps are stored away and locked by the mechanical lock in form of a hook.

You want to lower them, you put the flaps lever in the down position - the control valve opens for the extension chamber of the cylinder, it moves, after 3mm the lock is disengaged and then the whole mechanism starts to move, putting the flaps down to 50°. The pressure in the system is 32bar.

Now you put the lever in neutral, both chambers are emptied to atmospheric pressure, meaning as you lower the pressure in the extension chamber of the actuation cylinder, the flaps slowly come up. (They won't really come down as you slow down, though.)

You put the lever into the up position, the compression chamber of the cylinder gets pressurized, the flaps go fully up and lock behind the mechanical lock.

You now put the lever into neutral, and both chamber empty again.

 

Nowhere in the Yak manuals I could find anything indicating that the full 32bar of pressure were insufficient to bring down the flaps fully at any speed, or that the use of flaps for anything except landing was cleared.

Also, in the early Yak manuals I could find no relieve valves of any sort, so that the compression of flaps as we have it in game would invariably increase pressure in the entire system, which is designed to operate at 32bar. Not more.

Of course it is possible that the whole system was leaking so badly, that overpressure was no issue, in case of which extended use would cause problems for the compressor, which wasn't designed to continuously compensate for high losses of air.

[NachtJaeger110]

technochat: "flaps rods jammed" between 680 and 780 km/h in a dive, roughly the same time the ailerons remove themselves. It seems they just gave the flaps exactly the same strengh as the control surfaces 

[indiaciki]

noticed minimal speed loss when applying full flaps in a ju-87 during dive turn into final. deadstick landing. More lift -yes. los of airspeed - none - drag????

 

(Full flaps at 30s - you can hear it)

 

Edited August 26, 2015 by indiaciki

[Dakpilot]

Set up a Stuka in level cruise at 200kmh engage autolevel, when airspeed stable, deploy flaps observe results = loss of airspeed = drag, I think in your vid it is not so easy to tell how stable is rate of descent/AoA  which will effect airspeed

 

Cheers Dakpilot

[6./ZG26_5tuka]

I can imagine that at that kind of configuration your flaps basicly work like air brakes (+ the additional lift). Telling from own expirience those primarily increase your sink rate but do not influrence speed that much during landing.

 

Also talking to some real motor plane pilots I learned that once you extent your landing flaps "the first thing it's gonna do is go is down". So the drag is there but does not effect horizontal speed as much as vertical speed at that kind of pitch angle.

 

Of course if you force the plane to fly level with flaps extendet (as Dakpilot pointed out) the drag works right against your speed vector, means it will result in noticebly decreasing in airspeed.

Edited August 26, 2015 by Stab/JG26_5tuka

[Bert_Foster]

From US YAK11 exploitation document. talks about uplocks and how they are disengaged I should get a similar one on YAK9 in the next day or so:

 

 

 

 

I am struggling to understand how you get Combat flaps at high speed without damaging something. The only time you can get this blow back effect is if the flaps are extended and you then select neutral. If you are in neutral and select Down then you are going to get the system delivering full system pressure and attempt to drive the flaps to the full down position.

 

The YAK3 Blow back retraction

Its a different case in the go around as stated in the YAK3 manual. In that case you already have the flaps in the Down position, selecting neutral removes the air and the flaps then can blow back under increasing air load .... i guess until they get closed enough for the uplocks to engage. The YAK3 manual implies that this technique can result in full flap retraction. ..... so what prevents the same full flap retraction in the YAK1 if the lever is left in neutral ? .

Edited August 26, 2015 by Bert_Foster

[Maxyman]

From US YAK11 exploitation document. talks about uplocks and how they are disengaged I should get a similar one on YAK9 in the next day or so:

Yak-52 has the same system: double ended cylinder and flap up locks.

 

Yak-9 manual is available on the internet.

[Bert_Foster]

Yak-9 manual is available on the internet.

 

Got a link ?

Edited August 27, 2015 by Bert_Foster

[indiaciki]

Yak 1-9 intructional film:

 

[6./ZG26_5tuka]

Yak-9 manual is available on the internet.

 

Got a link ?

Yak-9U manual: http://www.avia-it.com/act/profili_daerei/libretti_velivolo/PA_libretti_PDF/Yak-9U.pdf

 

Technical Yak-1 manual: http://www.avia-it.com/act/profili_daerei/libretti_velivolo/PA_libretti_PDF/Yak-1.pdf

[Quax]

A couple of charts from RAF test document AVIA 6/2422 in the UK archives. These are on a study on the affects of flap on Spitfire Turn performance. Various flap angles were tested. The stuff shown here is for a flap angle of 30degrees. Spit flap was a split flap similar to YAK 1. this might be relevant to the current debate.

 

The Fan plots shown are similar to modern Fan plots (Dog house plots in US parlance). The "Line of zero climb " is effectively Ps=0 or the sustained turn performance boundary.

 

 

What can be seen is flap 30 does provide an improved sustained turn rate (smaller turn time). 

Taking the intersection of Ps=0 line with the lift limit gives a turn time clean of around 19secs (18.84deg sec).

Looking at the same point with Flaps 30 gives a Turn time of around 17secs (21.2 deg sec).

 

What can also be seen is that Flap 30 results in a reduction in Sustained G of 0.2g. i.e. Max sustained G Clean is 3.0g whilst with Flap 30 is around 2.8G

 

 Fan plot showing Flaps at 60deg and 85deg

 

one more chart

 

 

 

@Kwiatek:  Did you respond to this post already ?  Or do you claim the Spitfire FM arcadish as well ? Do you have similar charts for the Yak, that proof, that it should have much different behaviour ? As I understand, the flap design of the Spitfire resemble the Yak´s design much more, than f.e. the german design. (split flaps) 

 

Without charts and math this whole discussion is so pointless. There are too much variabels in the equation for the sustained turn times. 

Edited August 27, 2015 by Quax

[303_Kwiatek]

Eneregy is the key. Plane with flaps down will lose energy much quicker and will lost alt.  Plane with clean config would be able to make climb in turn when plane with flaps down ( expecially full down) will lose energy and alt trying to keep plane with clean.  So generally i think Spitfire with flaps up (clean) would end at the tail of  Spitfire with flaps down

Edited August 30, 2015 by 303_Kwiatek

[Quax]

Eneregy is the key. Plane with flaps down will lose energy....So generally i think Spitfire with flaps up (clean) would end at the tail of Spitfire with flaps down

You didn't answer to the facts. You just repeat your personal opinion. The charts proof, that the Spitfire did have a shorter turn time with flaps. You have to proof, that this charts are wrong, if you want to make a point.

 

"Plane with flaps down will lose energy." The shorter turn times are flown at a lower speed. Drag is a function of the speed. Your statement is again only your personal opinion. Devs have to rely on math and facts, not opinions. As I heard, they have lots of data, especially of the russian planes.

 

If you call the behaviour "arcadish", without coming up with any data, only based on your subjective opinions, i think that is not helpful.

Edited August 31, 2015 by Quax