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Approach Speed in GA Aircraft

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Approach Speed in GA Aircraft

Old 10th Sep 2020, 15:42
  #41 (permalink)  
 
Join Date: Jul 2014
Location: Scotland
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Originally Posted by Maoraigh1 View Post
"Average SEP 65/70 knots ...end of.
If I approach at this speed in my SEP, I will usually go through the far hedge unless I have the good sense to go around and try again at the correct approach speed for my aircraft (around 50 knots.)"
​​​​​​Can the approach speed in a low-inertia aircraft be too high, provided the "at threshold" speed is achieved? It can be too low.
OK, Maoraigh1, I know I can approach a bit faster and usually slow it down in the last couple of hundred feet (and will do so if it is very gusty). However, I find that a stable approach of 50 knots on finals (in a Kitfox 5, which, like all Kitfoxes, is slippier than it looks) usually leads to a better landing probably for the reasons outlined by Fl1ingfrog.

So yes, the approach speed in a low-inertia aircraft can certainly be too high!
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Old 10th Sep 2020, 16:47
  #42 (permalink)  
 
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a Kitfox 5, which, like all Kitfoxes, is slippier than it looks
Flying a Kitfox derivative, but not being a native English speaker, I find this phrase fascinating and a bit bewildering.
How do you define or describe a "slippy" aircraft?
What is the relation between a plane's appearance and its "slippiness"?
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Old 10th Sep 2020, 17:43
  #43 (permalink)  
 
Join Date: Jul 2014
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Originally Posted by Jan Olieslagers View Post
Flying a Kitfox derivative, but not being a native English speaker, I find this phrase fascinating and a bit bewildering.
How do you define or describe a "slippy" aircraft?
What is the relation between a plane's appearance and its "slippiness"?
Sorry to have confused you. Maybe I should have said more slippery or less draggy!

However, imho slippy looking aircraft tend to have short, smooth and thin wings, small and/or very closely spatted wheels, fairings where two surfaces meet and all gaps sealed as much as possible.

They do not tend to have long, thick, fabric-covered wings, very large wheels and tyres, struts, not many fairings and large gaps at the front of the control surfaces. These features are typical of the Avid Flyer and it's derivatives.

Nevertheless, what I was trying to convey was that they will float a long way on rounding out if you approach 10-15 knots too fast.
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Old 10th Sep 2020, 18:10
  #44 (permalink)  
 
Join Date: Jul 2010
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Ok, thanks, and no need to apologise! I have always thought my Apollo Fox a very nice compromise on all those factors, certainly for the beginner pilot that I consider myself. And yes, I found I can land on 200 metre runways, but then I must be really sharp on the approach speed.
Witness my first and only crash, luckily to very limited harm, when I was too high and one second later too fast when landing at Liernu EBLN - and one second late in realising I'd been better to go around.
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Old 10th Sep 2020, 20:35
  #45 (permalink)  
 
Join Date: Oct 2007
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Fast Approach in a tailwheel Jodel.

ASI top left is in knots
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Old 11th Sep 2020, 03:32
  #46 (permalink)  
 
Join Date: Jan 2020
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I assume the topic poster, like like majority people around the world, is flying in at least 20 years old aircraft (I fly in 60 years old C172A).
Regardless, after so many years of use I wouldn't trust 100% what's written in the POH/AFM, neither I would trust gauges (although I always do sanity check by comparing with GS).
The only way to test the stall speed it is to climb above 3000ft, then slow down and note down when it stalls.
Still, no ground effect up in the sky, neither air density/pressure/temperature is the same, neither every day is the same, but the Vso value should be very close to what's in the books.
Regardless, my safety speed is Vso 35kts x 1.404 which is 49kts, but I normally approach with 60.
Unless STOL aircraft or an aircraft with STOL modifications, I wouldn't be experimenting too much
Safe landings !
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Old 11th Sep 2020, 05:37
  #47 (permalink)  
 
Join Date: Oct 2004
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Originally Posted by Pilot DAR View Post
The yellow arc on some airspeed indicators is not necessarily related to Va. Va will generally be slower than the bottom of the yellow arc. Va is the maximum speed at which the pilot could overstress the plane with large pitch control inputs. Slower than that speed, a large control input would result in a stall, which would automatically unload the stress on the wings. .
Mmmm....
Va is a design speed, it does not vary with weight. The only time Va has any relationship to stalling in FAR 23 is if Va is chosen to be Va min.
I am aware of many aircraft manuals giving Va for weight. FAR 23 is clear, Va is determined at the design weight. These operating manual "Va's" are really more like VO, but I have no idea how they have been determined.

Below is a cut and paste of AC 23-19A which is very clear in the lack of relationship between Va, stall and structural strength - except in one particular circumstance, that if the designer decides to us Va=Va min

"48. What is the design maneuvering speed VA?

a. The design maneuvering speed is a value chosen by the applicant. It may not
be less than Vs√ n and need not be greater than Vc, but it could be greater if the applicant chose the higher value. The loads resulting from full control surface deflections at VA are used to design the empennage and ailerons in part 23, 23.423, 23.441, and 23.455.

b. VA should not be interpreted as a speed that would permit the pilot
unrestricted flight-control movement without exceeding airplane structural limits, nor
should it be interpreted as a gust penetration speed. Only if VA = Vs √n will the airplane
stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where
VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would
exceed the limit load factor.

c. Amendment 23-45 added the operating maneuvering speed, VO, in 23.1507.
VO is established not greater than VS√n, and it is a speed where the airplane will stall in a nose-up pitching maneuver before exceeding the airplane structural limits."

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Old 11th Sep 2020, 09:00
  #48 (permalink)  
 
Join Date: Nov 2005
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Originally Posted by zzuf View Post
Mmmm....
Va is a design speed, it does not vary with weight.
OK Va is the design manoeuvring speed but the operating manoeuvring speed does vary with weight which is important to understand. I have edited this because on reflection I think you explained it with the reference to the AC. Going through some AFMs I see this conflation of Va and Vo you mention so it is a good point you have raised.

Last edited by oggers; 11th Sep 2020 at 09:58.
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Old 11th Sep 2020, 15:02
  #49 (permalink)  
 
Join Date: Jul 2014
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Originally Posted by Maoraigh1 View Post
ASI top left is in knots
ASI​​https://youtu.be/06Clghh329g
Impressive but I prefer a stable approach of around 50 knots at the 230-530m grass strips I typically fly my Kitfox from.
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Old 17th Sep 2020, 13:47
  #50 (permalink)  
 
Join Date: Mar 2014
Location: Way north
Age: 43
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Piper 28-181 Archer II.

Approach speed 66 knots.
Stall speed fully loaded 53 knots.

I usually do the base at 76 and downwind at 86... don't know why... but someone taught me to add 10 knots from the final back in the day.

I would do less than the 66 when approaching a short runway.... we have winglets installed, and the damn aircraft tends to float..... a lot..... if you're a bit too fast.
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