Stall speed - gear up vs gear down

O2 Birddog said:
Well when they lack enough thrust to keep climbing they tend to flip over and come down nose first at a very high rate of speed.

The point is, if you apply enough thrust you can make a brick fly, thus thrust counters increased drag.

Drag does not apply only to the airfoil it applies to the entire airframe which is why high speed/high performance aircraft designers tend to reduce drag as much as possible.

You'll also notice some incredible aerobatic aircraft that have enough thrust to continue climbing virtually straight up or as some of our more interesting late WWII era aircraft proved take off standing straight up on their tails. Yes there were several propeller driven aircraft in this category.

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So going back to your post about rockets.

can you explain how that’s relevant to this discussion? How does an increase in parasite drag change the critical angle of attack?
 
Tarheelpilot said:
Say what?

you actually proposing that the drag on an arrow is the same gear up and gear down?
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I'm saying the opposite.

Gear down creates additional drag, that's why the new Diamonds allow the use of landing gear at cruising speed to be used as a speed brake.
 
Tarheelpilot said:
So going back to your post about rockets.

can you explain how that’s relevant to this discussion? How does an increase in parasite drag change the critical angle of attack?
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The entire subject was brought up because I said that thrust is/can be used to counter drag thus maintaining the same climb and angle of attack.
 
O2 Birddog said:
The entire subject was brought up because I said that thrust is/can be used to counter drag thus maintaining the same climb and angle of attack.
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But thrust doesn’t change the critical angle of attack. That’s when a wing stalls. Adding power doesn’t change that at all. Your rocket example means nothing in this conversation. No one here has a rocket strapped to the airplane. We all fly aircraft that rely on aerodynamic lift to fly. Rockets don’t. And those pictures are not of WWII era aircraft.
 
Tarheelpilot said:
But thrust doesn’t change the critical angle of attack. That’s when a wing stalls. Adding power doesn’t change that at all. Your rocket example means nothing in this conversation. No one here has a rocket strapped to the airplane. We all fly aircraft that rely on aerodynamic lift to fly. Rockets don’t. And those pictures are not of WWII era aircraft.
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Actually it does as the vertical lift aircraft and aerobatic aircraft demonstrate with propellers, not rockets.
 
O2 Birddog said:
Actually it does as the vertical lift aircraft and aerobatic aircraft demonstrate with propellers, not rockets.
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No. It doesn’t. All of those examples demonstrate that if thrust exceeds weight the vehicle will climb. It is not producing lift from an airfoil and there is no such thing as a stall speed.
 
Tarheelpilot said:
No. It doesn’t. All of those examples demonstrate that if thrust exceeds weight the vehicle will climb. It is not producing lift from an airfoil and there is no such thing as a stall speed.
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And without that thrust it is not possible thus the thrust lowers the stall speed to essentially a negative number.

It's ok we're far afield now derailing the thread, you guys continue on.
 
O2 Birddog said:
Actually it does as the vertical lift aircraft and aerobatic aircraft demonstrate with propellers, not rockets.
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Dunning Kruger in action. Did you get a lot of participation trophies as a kid?
 
Pi1otguy said:
In most planes the gear move the CG slightly. Doesn't stall speed change slightly with CG shifts?
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I don't know about that but I do know the turbulence they cause increases drag and affects lift which is why high speed, high performance aircraft were given retractable landing gear even though retractable gear causes a lot of crashes.
 
O2 Birddog said:
I don't know about that but I do know the turbulence they cause increases drag and affects lift
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The W&B for a Piper Arrow includes a small moment change for gear retraction.
Look up the POH for a 172. There's a 1 or 2 kt difference in stall speeds for forward and aft CG. I can't perceive 51 vs 52 KCAS on steam gauges, but perhaps someone better than me did during testing.
 
Pi1otguy said:
The W&B for a Piper Arrow includes a small moment change for gear retraction.
Look up the POH for a 172. There's a 1 or 2 kt difference in stall speeds for forward and aft CG. I can't perceive 51 vs 52 KCAS on steam gauges, but perhaps someone better than me did during testing.
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I'm not doubting you at all, I just don't know all the in's and out's. If you just look at the principle of how a lever works it makes perfect sense that the additional drag from the gear would create at least a slight nose down pitch and corresponding shift in CG.

I have a great deal of experience and some expertise when it comes to drag and it's effects on projectiles and thrust being able to compensate for drag but not all the finer points of drag and it's affects on aircraft.
 
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O2 Birddog said:
And without that thrust it is not possible thus the thrust lowers the stall speed to essentially a negative number.

It's ok we're far afield now derailing the thread, you guys continue on.
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That’s not how that works but you are correct, there is no point in continuing the discussion.
 
Tarheelpilot said:
That’s not how that works but you are correct, there is no point in continuing the discussion.
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Thrust eliminates stalling even though all control surfaces have enough airflow to be active at 0kts ground speed as noted in transition, takeoff, and landing.
 
O2 Birddog said:

Thrust eliminates stalling even though all control surfaces have enough airflow to be active at 0kts ground speed as noted in transition, takeoff, and landing.
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I understand what you are saying. No need for the video. You’re still wrong. The stall speed of that wing in the VTOL airplane is not zero. That is never possible. In fact at all of the regime’s you mentioned the wing is stalled.

Furthermore if we put aside you complete lack of understand regarding basic aviation terminology I’m still trying to understand how the capability of a one off x-plane and the vertical penetration of a small number of unlimited class aerobatic aircraft have any bearing whatsoever on this particular conversation.
 
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Tarheelpilot said:
I understand what you are saying. No need for the video. You’re still wrong. The stall speed of that wing in the VTOL airplane is not zero. That is never possible. In fact at all of the regime’s you mentioned the wing is stalled.

Furthermore if we put aside you complete lack of understand regarding basic aviation terminology I’m still trying to understand how the capability of a one off x-plane and the vertical penetration of a small number of unlimited class aerobatic aircraft have any bearing whatsoever on this particular conversation.
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This side line was because someone said you could not compensate for additional drag with more thrust.

All control surfaces have positive airflow at all speeds as demonstrated in the maneuvers due to that tremendous thrust.

The fact you don't understand or agree doesn't make it wrong, the flight demonstrate that it is correct.
 
O2 Birddog said:
This side line was because someone said you could not compensate for additional drag with more thrust.

All control surfaces have positive airflow at all speeds as demonstrated in the maneuvers due to that tremendous thrust.
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The original question was how does a gears position change stall speed. An actual flight test engineer has answered that question up thread.

Your contribution is if you have enough thrust it don’t matter cause you can hover.

I’ll say this slower and see if you actually listen. The wing is stalled in the example you are citing.
All wings have a critical angle of attack that when exceeded are stalled and do not produce meaningful lift. If the airplane is hovering and using vectored thrust for control it’s not flying in the manner being discussed in this thread.
 
Tarheelpilot said:
The original question was how does a gears position change stall speed. An actual flight test engineer has answered that question up thread.

Your contribution is if you have enough thrust it don’t matter cause you can hover.

I’ll say this slower and see if you actually listen. The wing is stalled in the example you are citing.
All wings have a critical angle of attack that when exceeded are stalled and do not produce meaningful lift. If the airplane is hovering and using vectored thrust for control it’s not flying in the manner being discussed in this thread.
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There is no thrust vectoring in these aircraft. All the low speed maneuvers are performed using traditional control surfaces.
 
Tarheelpilot said:
Oh Christ you are clueless.


I’m out. It’s like talking to ****ing rain man.

72 toothpicks
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The rain man is the guy who doesn't understand you still have a great deal of positive airspeed and flow over the wings and control surfaces in one of these type craft even in a hover so no, technically the wings are not stalled.

For control surfaces to operate they must have that airflow.
 
O2 Birddog said:
The rain man is the guy who doesn't understand you still have a great deal of positive airspeed and flow over the wings and control surfaces in one of these type craft even in a hover so no, technically the wings are not stalled.

For control surfaces to operate they must have that airflow.
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In a hover you could remove the wings and it would still hover. The wings are contributing nothing to maintaining “flight”.

In regards to the control surfaces still “flying” sure. They are static in space but have airflow from the column of moving air being thrust by the propeller. So when they move that airflow is diverted and it’s possible to control the aircraft.

The exact same thing happens with a thrust vectoring nozzle on a rocket or jet engine. In fact an F-35 or Av-8 in hover mode is “flying” exactly the same way as your cited example but the aircraft is in a level flight attitude rather than a vertical orientation as your example. It works because the wing is not lifting anything. It’s just dead weight being carried by a thrust vector.

No matter how you spin the terminology in your head it does not change the fact that at zero airspeed that wing is not flying in any meaningful way. It’s staying aloft due to its excessive thrust and the vector of that thrust. Control is obtained through vectoring said thrust either by nozzle or control surfaces in the slipstream. EDIT: plus any lift that is getting generated from slipstream flow off that prop is perpendicular to the chord line of the wing so it will cause a lateral translation in a hover. It doesn’t do anything to maintain flight. In fact it just crates a force that must be countered to maintain a static position.

AND it still has no bearing whatsoever on the original question. Regardless of the minutiae of our little side discussion your post is irrelevant to this discussion.

AND your proposed concept that an increase in thrust reduces the stalling speed of an airfoil is a clear indication you lack a fundamental understanding of how lift is produced.
 
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At high pitch angles there is a vertical component to thrust that offsets some of the aircraft's weight, thus the aircraft can fly slower at the same AOA. The difference will be small, a couple of knots for most conventional airplanes.

If the aircraft has enough thrust available that it can actually hang on the prop, it's a different story and the AOA of the wing is meaningless. But getting to that point involves a transition through a regime where the wing is stalled but the pitch angle isn't enough to use thrust to hold the plane up, which is part of why it's so difficult to design and operate such aircraft.
 
Tarheelpilot said:
An actual flight test engineer has answered that question up thread.
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I lost track - are you referring to Dana or Martin, or both? I'm curious to the answer, and their posts make sense.
 
The best part of this thread is that the first reply by Llewtrah381 (no offense to him) was widely admitted to be wrong, even called "boneheaded" by the person who wrote it. And O2 Birddog "like"d it.
 
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