Region of reverse command

[paid4training]

Okay if you ask 5 different CFI's you may get 5 different answers. Are you in Region of reverse command during an landing approach or when you are in slow flight? I know there is an FAA "correct" answer but how can you practically instruct this to a new student? I guess because I HAVE asked several instructors this question and gotten several different answers I thought I'd ask here and see if be inlighted or more confused? I've heard it is 5% of stall speed is this true and any suggested reading regarding this issue?

 

[midlifeflyer]

For me, the region of reverse command is anything below best glide speed. For explanations, I'd start with the standard lift/drag graph that is in most aviation texts. Anything below L/D Max, the drag starts increasing as you get slower, so the power needed for level flight increases.

 

[Doozer]

I agree with midlifeflyer.

For those students who don't like or comprehend graphs, I tell them that from the point it begins to take more power to fly slower in straight and level flight, they're in the region of reversed command.

Hope this helps.

 

[mpflies2]

A way to visualize this as I was taught....

When you reach a speed where an increase in back pressure will increase the descent rate as opposed to a causing the airplane to climb. The reason for this being that you are increasing the AOA to a point where you decrease lift.

Anybody else taught this?

Marc

 

[midlifeflyer]

A way to visualize this as I was taught....

When you reach a speed where an increase in back pressure will increase the descent rate as opposed to a causing the airplane to climb. The reason for this being that you are increasing the AOA to a point where you decrease lift.

Anybody else taught this?

I think that teaching "reverse command" without the full complement of lift/drag and power is a problem.

FWIW, I think it's inaccurate. With back pressure alone, you can get slower and slower without descending, at least until you get to the critical AoA. You do it all the time in a level altitude power-off stall.

 

[Morettis]

What you guys are talking about is being slower then L/D Max, where it takes more power to overcome the rapid increase in induced drag as you fly slower. Reverse command is when you roll the ailerons right and the plane rolls left due to aerodynamic forces such as mach shockwaves and the wing bending from the force of the aileron.

 

[MauleSkinner]

I agree with midlifeflyer.

For those students who don't like or comprehend graphs, I tell them that from the point it begins to take more power to fly slower in straight and level flight, they're in the region of reversed command.

Hope this helps.

...Although you have to be sure to explain it so that what they HEAR isn't "If I add power, I'll go slower".

Fly safe!

David

 

[Amish RakeFight]

Are you in Region of reverse command during an landing approach or when you are in slow flight? I know there is an FAA "correct" answer but how can you practically instruct this to a new student?

The region of reverse command is encountered during the low speed phase of flight such as an approach to land or during slow flight manuevering.

The premise behind the region of reverse command is that it takes a greater amount of power to fly at a slower speed than would normally be required as in the region of normal command. This region is occupied between the stall speed and the best endurance speed.

The best endurance speed, which is the lowest power setting required to maintain level flight, is the dividing line between the region of normal and reverse command. Speeds below this demarcation will require an additional amount of power in order to maintain a speed slower than best endurance speed.

This greater amount of power that is required occurs because there is an increase in induced drag. The higher power setting is required to produce enough thrust to counter this induced drag in order to maintain level flight.

 

[The_Russian]

Correctons.....

What you guys are talking about is being slower then L/D Max, where it takes more power to overcome the rapid increase in induced drag as you fly slower. Reverse command is when you roll the ailerons right and the plane rolls left due to aerodynamic forces such as mach shockwaves and the wing bending from the force of the aileron.

This has nothing to do with the region of reverse command. Any shockwaves produced by aircraft are only made with Mach .02 of the speed of sound (approx). The reason inboard ailerons or spoilers are used instead is a reduction inoverall force required by the aircraft. It takes more force to operate an outboard aileron than a spoiler or inboard aileron. Also, an airliner is designed to be stable during low speed flight. So engineers do not put very much design wing twist along the span of the wing. Due to the length of the wing and the lack of built in wing twist, if outboard ailerons are used excessively, the aerodynamic forces will force its ow twist on the wing. This would cause the outboard section of the wing to bend in the oposite direction of the pilot's turn.

For me, the region of reverse command is anything below best glide speed. For explanations, I'd start with the standard lift/drag graph that is in most aviation texts. Anything below L/D Max, the drag starts increasing as you get slower, so the power needed for level flight increases.

It is true that as you pass through L/D max, you enter the region of reverse command. Induced drag varies inversely with the square of airspeed. So what I am sayin' is that if the airspeed is cut in half, induced drag quadruples. At this point you would need more power to maintain altitude for that airpeed as airspeed decreases below L/D max. For the region of reverse command to be fully "true", the aircraft needs to stay at the same power setting. For example: if the nose is lowered at X power setting at the same rate as the dynamic stability for that aircraft (assuming it is positive), the aircraft will gain altitude. This is mostly due to the increase in airspeed creating the climb.

Power for altitude, Pitch for airspeed below L/D max!

 

[The_Russian]

The region of reverse command is encountered during the low speed phase of flight such as an approach to land or during slow flight manuevering.

The premise behind the region of reverse command is that it takes a greater amount of power to fly at a slower speed than would normally be required as in the region of normal command. This region is occupied between the stall speed and the best endurance speed.

The best endurance speed, which is the lowest power setting required to maintain level flight, is the dividing line between the region of normal and reverse command. Speeds below this demarcation will require an additional amount of power in order to maintain a speed slower than best endurance speed.

This greater amount of power that is required occurs because there is an increase in induced drag. The higher power setting is required to produce enough thrust to counter this induced drag in order to maintain level flight.

Good addition!