Optimal landing speed

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rwtucker
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Re: Optimal landing speed

Post by rwtucker »

pietromarx wrote:While the DA40 is famous for floating. . .
I guess it is a matter of perspective. For me, the DA40 is the less inclined to float than most of the aircraft I have flown. I find it a little like the Hershey Bar Cherokee in that chopping the power executes a landing if your numbers are close. In my limited experience, the long wing PA28s (other than the nose heavy 235) are serious ground effect floaters. Short of sticking them on the ground (and risking a bounce) you can't get on the runway if you are a few knots fast, such as you would be for gusts. We used to take bets on how long it would take to come down if we were fast across the threshold.
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pietromarx
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Re: Optimal landing speed

Post by pietromarx »

Fair enough. I haven't found the airplane to float too much, but I've had a lot of folks tell me they think it does!
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Lance Murray
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Re: Optimal landing speed

Post by Lance Murray »

There are 5 pages of discussion on what airspeed to fly on landing. I'll be honest in saying I don't have a clue what my airspeed is. I look out the window, feel the stick and listen to the sound. Use the Force. Learn to fly it onto the runway WITHOUT the air speed indicator. Practice that and I guarantee that your landings will improve.

Remember that it is not about IAS. Angle of attack is what is important.
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rwtucker
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Re: Optimal landing speed

Post by rwtucker »

Lance Murray wrote:I'll be honest in saying I don't have a clue what my airspeed is. I look out the window, feel the stick and listen to the sound. Use the Force. Learn to fly it onto the runway WITHOUT the air speed indicator. Remember that it is not about IAS. Angle of attack is what is important.
I thought I was the only one Lance. Somehow, looking at IAS seems like the wrong thing to do on final. The last time I look at it, and only then in certain circumstances, is on my base-to-final turn. Just for fun, I have had the right seat call out the IAS along final. It varies quite a bit with load, wind conditions, length of runway, which turnoff I want, etc.
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Re: Optimal landing speed

Post by Antoine »

Well I'm glad that the discussion is taking this turn. So I'm coming out with two things that struck me and one possible explanation for this discussion

1) I normally don't look at the ASI anymore once the airplane is on the correct path. It is very much what Lance described. The only situation where I do keep airspeed in sight is in heavy winds.

2) With all due respect for the people who keep some power, I only use power to adjust my aiming point and correct for unexpected changes in wind conditions. Apart from that it is a power off glide starting as soon as I feel the engine is no longer needed - typically 50 m / 150 feet before threshold.I only do this in the DA40 btw.

3) When I was a student pilot, my instructor was unable to give me the "facts" I needed as as starting point for my own adjustments. I felt overwhelmed until I asked another one who obliged.
This is exactly what we are fixing here: giving Sara the facts for her to start from.
Eventually she too will fly the DA40 by visual and "butt-o-matic" clues, but I very much understand and can relate to the need to put numbers on phases of flight.
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Re: Optimal landing speed

Post by Colin »

"An angle of attack instrument? If you don't know your angle of attack you have no business being in the plane." – Chuck Yeager, possibly a little grumpy now from years without enough speed
Colin Summers, PP Multi-Engine IFR, ~3,000hrs
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rwtucker
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Re: Optimal landing speed

Post by rwtucker »

Lance Murray wrote:Remember that it is not about IAS. Angle of attack is what is important.
Given the design of our stall warning system, especially the fact that it produces analog output in contrast to the binary output typical of the stall switch on the leading wing edge of many GA aircraft, it would seem possible to derive a signal from the pressure tube to drive an AOA indicator which could then be calibrated. My physics background suggests that this is a possibility using a small electro-mechanical transducer inserted in line just before the stall tube reaches the toy plastic stall horn. It is not difficult from there to design a simple three or four color LED array driven by the signal. Do any of our engineers have a comment on the practical side of this idea? I'm setting the regulatory issues aside at the moment.
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Chris B
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Re: Optimal landing speed

Post by Chris B »

rwtucker wrote:Given the design of our stall warning system, especially the fact that it produces analog output in contrast to the binary output typical of the stall switch on the leading wing edge of many GA aircraft
Hi Robert -

Hopefully others will chime in on the feasibility of your idea.

But IMO the existing "analog" stall horn is a very useful audio-only AOA indicator for approach & landing, and compensates for variable aircraft weight. Per my earlier post, IME a "chirping" stall warning horn indicates on-speed for short final. A blaring horn is too slow, while a silent horn is too fast. No zippy digital display, but I find the audio cues very helpful while keeping watch outside for traffic.

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Tom Davis
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Re: Optimal landing speed

Post by Tom Davis »

This conversation has probably been the most helpful thing I have seen on DAN. It has been great. Thanks to all of you.

Tom
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Re: Optimal landing speed

Post by tonylee »

Antoine wrote:Hi Sara

From my experience, the DA40 has a narrow "sweet spot" for landing speed, weight dependent:

At MTOW I go for 70 KIAS at the gate
Very light, it's 65

If you come in too fast, you need to master the art of flying close to the runway in ground effect and letting speed bleed out - the plane will ultimately want to settle down.
As you feel this about to happen you should pull up gradually to dampen the touchdown. This is good in calm winds but risky in gusty conditions.
I am sure you noticed that a touchdown with excess energy will be punished by a nasty bounce.

If you come in too slow, the controls become mushy and as you said the stall is abrupt. What you want is to be so close to the runway when you stall to make the event imperceptible! ;) takes some practice!

Here's what I would try: come in slow, but with a predicted touchdown point a bit further down the runway.
This way, you won't have to stretch the remaining energy to "reach" for the runway.
A successful full stall landing close enough to the runway is impressive: the plane has so little energy left that it almost stops right after touchdown.

My preference is to nail the speed and allow some safety margin by means of the displaced touchdown point.
And let us know when you achieve a real greaser!
I want to thank Antoine for this post. I have not posted in a while and have not been flying much in past couple of years. I had a prop strike last year on landing. I porpoised the landing which led to a lot of anxiety about the plane. While the plane was being fixed and engine inspected I thought about selling the plane and ending my flying for good. I picked up the plane with my CFI and practiced several landings. None of which were good. I was so scared that my CFI flew the plane back with me to my airport then I drove him 2hrs back to the first airport. I have had this plane since 2011 so it not like any of it is new to me. I continued to practice landings with my CFI but not progressing like I hoped. I used to land the plane fine a couple of years ago but after the accident my anxiety was taking over and I would flare too high and kept dropping the plane out of the sky and bouncing down the runway. I was getting very frustrated over the situation and my CFI wasn’t really great at flying a DA40 and when he tried landing the plane, he bounced it also. I went back and read this thread last week and it clicked. I did exactly what Antoine said and I allowed myself to let the plane land down the runway on it’s own rather than flaring too much and dropping the plane. I performed 6 beautiful landings today even with a bit of crosswind and settled down my anxiety. I am no longer afraid of my own plane and am very grateful for this advice.
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