Uncontrolled arrival, La 5

[HagarTheHorrible]

The Pe-2 is a bitch to land. 

 

I had an expectation that the La-5 would also be much the same.

 

I started a topic about this several months ago, long before we got our sticky mits on the La-5, but thought it might be interesting to discuss it further now that we have something to evaluate.

 

I have a quote from "The illustrated Encyclopaedia of Aircraft", a magazine that I collected during the 1980's.  The quote goes as follows "and every landing was an almost uncontrolled arrival marked by prolonged bouncing.  Pilots with nerve to let the bounces subside survived; those who suddenly added throttle crashed inverted."

 

As is probably painfully obvious I have no expertise about aerodynamics generally or about the La-5 in particular, but I got to thinking why the above quote might be the case.  Given it's lineage I had thought that maybe the LaGG 3 might have had similar problems but actually I think it provides the control that might give us the answer to the above quote. 

 

From a layman's perspective I think what was going on was.  The La-5 used an airframe that was designed for a heavier, less powerful, liquid cooled engine. The radial engine used, was lighter and more powerful than the engine the airframe was designed for, this was exacerbated by all the other structural lightening that took place.  I think this combination of a lighter airframe and engine meant that, aided and abetted by ground effect that unless the aircraft was perfectly stalled into a three point landing there would still be too much lift under the wings and without the weight of the liquid cooled engine all the way at the front end to hold it down the nose would lift and several bounces would result, it was possibly less a case of bouncy bounces and more of floaty bounces with a nose high attitude.  This may very well have felt far more dramatic from the cockpit than it appeared to someone watching from the ground.  The controls however had insufficient authority, again exaggerated by the much lighter overall weight of the aircraft to counter the torque of the engine at full power, so if the engine was opened up to attempt to regain some sense of normalcy the aircraft would roll either onto a wing tip or possibly in the worst cases right onto it's back.

 

Obviously this begs a question about the BoS La-5, exactly what that question is I don't know, maybe someone who understands these sort of things better might.

[AndyJWest]

I don't think that the early La-5s were any lighter than the LaGG-3s - and aerodynamics limits the extent to which the centre of gravity of an aircraft can be changed without making it uncontrollable. The difference as far as BoS versions are concerned is that the La-5 has leading-edge slats. 

[[JG2]R7_Blackadder]

I do think the La-5 engine just balanced the initial underpowered airframe LaGG was using. I'm sure there will be plenty of responses by those who have better technical knowledge but I do think your concerns are "superficial" Hagar.

 

All in all what I read about it was about a much friendlier aircraft as the Yak could be, opposed to the kinds of the MiG-3.

[HagarTheHorrible]

I don't think that the early La-5s were any lighter than the LaGG-3s - and aerodynamics limits the extent to which the centre of gravity of an aircraft can be changed without making it uncontrollable. The difference as far as BoS versions are concerned is that the La-5 has leading-edge slats. 

 

You're right, I don't know where the notion that they had also lightened the airframe came from.  Also when I say lighter engine I should clarify I mean the whole power plant and ancillaries and not just the engine.

 

 

I do think the La-5 engine just balanced the initial underpowered airframe LaGG was using. I'm sure there will be plenty of responses by those who have better technical knowledge but I do think your concerns are "superficial" Hagar.

 

All in all what I read about it was about a much friendlier aircraft as the Yak could be, opposed to the kinds of the MiG-3.

 

 

It sure doesn't feel superficial in the Pe-2.  It seems the La-5 was tricky to take off and land, quite possibly caused by more torque than the control surfaces could reasonably handle at low speed.  If the FM's are physics based then it suggests something is awry, does it not ?  It was interesting to note that when Quax interviewed a Veteren 109 pilot and let him have a go of BoS, one of the comments was when taking off (might have been landing)  the BoS 109 needed half rudder while in real life he said it needed full rudder.  This begs the question are the two things connected ?

Edited May 11, 2014 by HagarTheHorrible

[senseispcc]

For me the LA 5 is easier to land than the Lagg3 only because it is more stable at low speed! The weight difference is only 50Kg the La5 being the heaviest. The big difference in engine power output the La-5 a 1676 hp M-82 radial engine and 3300 kg weight the Lagg-3 series 29 a 1210 hp and a weight of 3280 Kg so the weight is not a explication but the slats it the wings make a big difference and so does the power supplement.

 

Secondly the PE-2 is a two engines plane it landing handling is not the same at all than a single engine fighter, first not like for the fighters never deploy the full flaps, secondly the landing distance is a lot longer use brakes if you want and do not try to make a three point landing!

 

[[JG2]R7_Blackadder]

Kiershar is right, also maybe the FM is not final and more tests are needed.

 

Sure I will have a look this evening if I can find anything about it

Edited May 12, 2014 by [JG2]The_Blackadder

[Crump]

Pretty much every single-engine plane is gonna bounce on landing if you don't flare enough. You have to be really experienced in landing physics to be able to have your wheel touch the ground only once, usually much easier to do with a velocity vector.

 

Absolutely.  Most prop strikes begin with bouncing on touchdown and botching the recovery with the pilot incorrectly trying to dampen the oscillation with control input.  He bounces up, so he pushes forward and then pulls back going back up again.  He realizes he is trouble too late, hits the power for a go around and runs into the dirt barrier.

 

To me it sounds like a pilot training issue and not necessarily an "La-5" design problem.