Turnbacks
Join Date: Jan 2005
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Regarding
There are two areas where it does:
First, the visual cues change dramatically at low heights; if you fly competent aerobatics at altitude, it will take a good while to reduce your operating height down to a couple of hundred feet for displaying.
Second, you may be introducing a fixed reference point on the earth into the equation, for example you may be flying an approach to a runway, following the glideslope. Thus, you are attempting to follow a path which remains fixed in a flowing medium (the air). You could liken this to trying to thermal in 30 kts of wind, following a path exactly over a large circle marked out on the ground beneath you...
On very windy days (the worst I've landed in was 65 gusting 75 straight down the runway), it is very noticeable that as windspeed decreases, thrust must be added, and vice versa. This is absolutely crucial to windshear recovery. The seat of the pants is also valuable; certain feelings in the nether regions on the approach have me adding 5 or 10% N1 before the instruments register any change.
On the topic of this thread in general...
Ahem...
QRH, please, internet discussions, thread drift checklist, recall actions!
I can't believe that proximity to the ground makes any difference
First, the visual cues change dramatically at low heights; if you fly competent aerobatics at altitude, it will take a good while to reduce your operating height down to a couple of hundred feet for displaying.
Second, you may be introducing a fixed reference point on the earth into the equation, for example you may be flying an approach to a runway, following the glideslope. Thus, you are attempting to follow a path which remains fixed in a flowing medium (the air). You could liken this to trying to thermal in 30 kts of wind, following a path exactly over a large circle marked out on the ground beneath you...
On very windy days (the worst I've landed in was 65 gusting 75 straight down the runway), it is very noticeable that as windspeed decreases, thrust must be added, and vice versa. This is absolutely crucial to windshear recovery. The seat of the pants is also valuable; certain feelings in the nether regions on the approach have me adding 5 or 10% N1 before the instruments register any change.
On the topic of this thread in general...
Ahem...
QRH, please, internet discussions, thread drift checklist, recall actions!
Join Date: Apr 2007
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Islander - I wasn't saying that losing speed in a turnback wasn't important! My grasp of the physics behind the whole inertial airspeed/groundspeed issue may need some work, but I have flown many simulated turnbacks (luckily no real ones, yet), and am very well aware of the vital need to maintain suficient airspeed for the turn. I was saying that I'm not sure the inertia issue is really key in the consideration of turnbacks. You might be well advised to do people the justice of reading what they actually write before you are so keen to rubbish what they say!
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I don't remember ever experiencing loss of airspeed when turning downwind. I was taught to maintain airspeed throughout the turn. In shallow angle of bank turns, airspeed usually reduces slightly because of the increased back pressure on the stick required to maintain altitude. In steep turns, the airspeed is maintained by applying power to overcome the back pressure on the stick.
I understand the loss of airspeed in an aircraft like a Harrier (which I have not flown) or helicopter (which I have) in the hover, but I believe that in other aircraft, in forward flight, the pilot should control the airspeed by using the stick. I don't recall, in another life, having airspeed changes imposed on me when flying holding patterns into and out of wind.
I also note in my old copy of "Flying Instructor's Handbook - Piston Provost" when teaching low flying, we were to "Fly into wind and turn accurately through 180 degrees. Fly downwind then turn accurately through 180 degrees. Maintain constant airspeed. Demonstrate in moderate wind conditions."
Have I the wrong end of the stick in this discussion? Is the loss of airspeed/downwind turn a theoretical rather than practical question?
I understand the loss of airspeed in an aircraft like a Harrier (which I have not flown) or helicopter (which I have) in the hover, but I believe that in other aircraft, in forward flight, the pilot should control the airspeed by using the stick. I don't recall, in another life, having airspeed changes imposed on me when flying holding patterns into and out of wind.
I also note in my old copy of "Flying Instructor's Handbook - Piston Provost" when teaching low flying, we were to "Fly into wind and turn accurately through 180 degrees. Fly downwind then turn accurately through 180 degrees. Maintain constant airspeed. Demonstrate in moderate wind conditions."
Have I the wrong end of the stick in this discussion? Is the loss of airspeed/downwind turn a theoretical rather than practical question?
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> I am sure from empirical means that the effects of intertia are very small.
In the case of circling in wind I agree. The rate of change of heading is too low.
..but it's worth remembering that if inertia didn't exist you could make a flat turn using rudder only with no skidding.
..or to put it another way that 45 degree bank is only needed because of inertia. That's half the lifting force of the wing needed to counteract it. Not so small eh?
In the case of circling in wind I agree. The rate of change of heading is too low.
..but it's worth remembering that if inertia didn't exist you could make a flat turn using rudder only with no skidding.
..or to put it another way that 45 degree bank is only needed because of inertia. That's half the lifting force of the wing needed to counteract it. Not so small eh?
