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Date: Wed, 06 Jan 1999 08:53:03 -0600
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Subject: Landing speed (was: C-150 to C-172 transition: Not trivial
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Tyler Kirby wrote:

> So the question begs itself, what speeds to use on approach? My POH 
> doesn't list conversions below 40 although stall is 31-33 KIAS. 

I believe you will find stall speeds in your POH given in CAS, if
you read carefully.

They are in my C150, C172, C172rg, C182rg etc POHs.  The Piper
POHs have a chart for the conversion.

> Luckily it does list approach speeds at 60 KIAS (40* flaps) 
> to 65 KIAS (0* flaps). 

I think you will find these speeds correspond to 1.3xVso in CAS.

> What about for those planes that don't list recommended stall speeds? 

I know of no POH which doesn't list stall speeds; they aren't a
"recommendation" but an observation.

> Seems like one could find Vso on their own but then to multiply 
> * 1.4? 

The FAA Landing Advisory Circulars and every other source I've
found (FAA Wings seminars, several CFIs with 12,000+ and 20+ years
experience) recommend 1.3xVso in CAS on final approach.
Don't take my word, go get the Landing Advisory Circulars from your
CFI or local FSDO, they're worth reading and free.

Tinkicker is the only source I've heard for the 1.4xVso recommendation.
Personally, I'm suspicious of dogmatic assertions given anonymously and
followed by "trust me, friend" rather than some source one can verify.

Approach speed doesn't matter all that much in a draggy plane like a
C150 or C172 (you might float more, but you'll still land in a 
reasonable distance).  But if you want to transition smoothly
to slicker, faster planes I think it is appropriate to follow
the 1.3xVso (CAS) recommendation on final AND ADJUST IT FOR WEIGHT
(stall speed varies with weight, multiply by sqrt(actual weight/gross
weight).  

Learn to fly the POH numbers consistantly and precisely, and add only
1/2 of any wind gust factor, no more, as long as flight conditions are
normal. 

This is especially critical if one likes to land on shorter runways,
ie runways only 20 or 30 percent longer than the figures in the takoff
distance table of the POH.

If I landed my plane at 1.4xVso, there is no way I could fly it safely
in and out of 2000 ft runways.  Following the POH and FAA advisory
circular recommended procedures precisely (1.3xVso in CAS), I can use
normal approach speeds and put it down easily in half the runway I 
need to take off.  If the question is "do 5-6 kts really make a
difference" the asnwer is "yes, they really do", in some planes more
difference than others.

Snowbird

