Landing gear's aerodynamic effect

[6S.Season]

First post for me, so i would like to start saying hi to everybody, I'm glad to be part of this huge flight simmer community! 

Back on topic, I have a doubt about the effect of lowering the landing gear on the Lagg. 

The only effect I noticed is the increase of aerodynamic drag, that is correct to me. 

But I also expect a change of pitch attitude, in particular the presence of a slight dive momentum, due to the increased drag in the lower part of the airplane.

Secondly I guess that the reduced aerodynamic efficency and the creation of vortex all around the landing gear's legs should generate a moderate shake effect on the entire airplane. 

The question is: is it correct to have only an increase of drag or we should expect also the other two effect mentioned above?

 

Ps: I hope you can easly understand my post: english is not my mother language and I'm sure I have made some mistakes! 

[Sternjaeger]

Hi Season, the drag element has been noticed before, regarding the shaking, I think it's a bit of an overdone (and wrongly assumed) representation of what happens in real life: shaking would normally be caused by a fluttering surface, and the landing gear is probably the most robust part of your aircraft, which surely wouldn't flutter, so you'd only have to expect a variance in pitch.

Edited November 25, 2013 by Sternjaeger

[6S.Season]

sorry, I didn't notice this http://forum.il2sturmovik.com/topic/2433-landing-gear-drag/

In any case I guess the drag effect is correct, as pointed out in the  post linked above the drag goes with the square of the speed, so at low speed the effect is minimum. 

My concern are more on the variance in pitch and the shake effect and I'm happy to know that you agree with me at least on the first issue! 

[DD_bongodriver]

there is definitely a buffeting that comes from extending undercarriage, given retractable gear is not covered in fairings and therefore very draggy it causes a bit of turbulence which is felt as buffet through the airframe, sometimes the gear doors could be subject to some fluttering often noticed as a humming vibration on some aircraft, it is also quite reasonable to expect some sort of pitching moment from the drag.

[Sternjaeger]

I agree on the pitch, but the buffeting? I guess it depends on which aircraft you're flying and the airspeed you're flying at, but don't you think that buffeting is a bit extreme Bongo? You can perceive a vibration or a bit of initial asymmetrical drag (especially if the opening is not symmetrical), but I'd be worried if my aircraft started buffeting as the landing gear came out! 

[DD_bongodriver]

Well I use the term buffet purely to describe the rough air flowing around the gear not saying the aircraft actually buffets like in a stall, every retractable gear aircraft I've flown has a noticeable noise and shake associated with gear deployment that is felt through the airframe.

[Sternjaeger]

ah ok, yeah than we're talking about the same thing! Yeah you'd get a subtle feeling, the perception of which is accentuated by the pitching, but it's far from the "shake shake shake" that we saw in IL-2 mods etc... it's more of a slight vibration.

[Finkeren]

I was actually pleasantly surprised to discover that the effect was as subtle as it is in BoS. I'm not a pilot myself, but I have flown in enough different kinds of aircraft to know, that there is no violent shaking or buffetting in even lighter aircraft, when the undercarriage is lowered, as many flight sims would have you believe.

[DD_bongodriver]

Well the gear configuration could make a difference, I have never flown a taildragger with retracts and certainly not a warbird, but purely from a aerodynamically sympathetic point of view I could easily see the long undercarriage legs of the typical warbird causing a higher degree of noise and vibration than a typical tricycle light aircraft and almost certainly a higher degree of pitch moment, but yes I would never see any reason for violent shaking but can't say I have ever experienced anything like violent shake in a sim either, maybe just down to how the individual perceives things.

[Furio]

I also have the feelings that undercarriage legs should produce noise only, while doors are a more probable source of vibrations. The Yak 7 V comes to mind, with fixed, unfaired gear. It was surely one of the fastest fixed gear planes ever built, but I was unable to find its actual performances. Usually, those reported are of the retractable gear version (Uti26).