C172 Instrument Approach Speed???

S

skysnake

New Member
Hi all, I am going to start my flying this week for my CFII. I have what I hope isn't a stupid question for all you "double eyes" out there.

What kind of approach speed would you use for a precision and non-precision approach? I am an AA Captain and check airman on the MD-80 and we use Vref plus 5 knots, plus any wind/gust additive. This same formula seems way too slow to fit into the real world in a light airplane. I do worry about flying an instrument approach to a short runway in the Cessna at or near the top of the white arc though. It seems like this could be a recipe for an overshoot on a short or wet runway.

Thanks a million for your ideas. I want to do the best job I can with the most information that I can glean.

Chris Boice
AA MD80 CA and CKA
 
I'm not a CFII, but, I did my instrument in a 172 this past spring. The school that I went to was a fan of flying 100 KIAS, regardless of the type of the approach, to minimum's. From there, it was a crap shoot, as to getting it slowed down. Power came out, flaps went in. Ideally, if it were up to me, I'd probably have picked right about 90 KIAS. I've seen other schools doing an ILS as slow as probably 70-75 in a 172. Pick whatever your comfortable with.
 
Most places and people use 100 until the FAF and then 90 with flaps 10 after, regardless of precision or non precision.
 
skysnake said:
This same formula seems way too slow to fit into the real world in a light airplane. I do worry about flying an instrument approach to a short runway in the Cessna at or near the top of the white arc though. It seems like this could be a recipe for an overshoot on a short or wet runway.
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At busier airports with long runways, approach is probably going to be asking for your best forward speed. 130 kts as long as you can in this case. If there is an MD80 behind you, safe to say you aren't going to run out of runway.

Typical ground roll for a 172 is about 600'. If you can get down to 70kts at 50' AGL it is about 810'.
 
When I was training for my IR and CFI-I I chose 100kts. Mainly because that is what we flew the pa-44 at. However this was all to runways more than 5k ft.
 
In general, 90 KIAS works well. The transition from approach speed to the landing configuration at minimums after "breaking out" really is not too difficult. Some visual practice would be beneficial for acclimating to the changing attitudes that accompany airspeed and configuration changes in the 172---not something you want to be experiencing the first time after an approach to minimums!

One teaching strategy is to perform the first few approaches at slower speeds---ATC, airspace, and other traffic pending---to become acquainted with the new procedures. Some have used 70 KIAS and 10 degrees of flaps for a leisurely ride down final, and with roughly 10 knots of headwind, the time calculations are again simplified.
 
Pilot Hopeful said:
....

One teaching strategy is to perform the first few approaches at slower speeds---ATC, airspace, and other traffic pending---to become acquainted with the new procedures. Some have used 70 KIAS and 10 degrees of flaps for a leisurely ride down final, and with roughly 10 knots of headwind, the time calculations are again simplified......
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I like that idea!

I will be incorporating that into my syllabus for students who fixate and fly the ILS at 120 kts.....I have been wondering how to break that behaviour--gently.

You have provided the answer.

Thanks.


b.
 
tgrayson said:
The most commonly used speed is 90 KIAS. It makes many of the timing calculations pretty easy and only 5 knots above the white arc.
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:yeahthat: Or 120 if you're at a big airport and are planning going missed and want to keep ATC reasonably happy.
 
I'd say train for normal approach speed, say 90 knots in a 172, and also train for maximum forward speed. Going into busy airspace there's a good chance ATC might ask you for maximum forward speed. You want to be ready for it.
 
juxtapilot said:
I'd say train for normal approach speed, say 90 knots in a 172, and also train for maximum forward speed. Going into busy airspace there's a good chance ATC might ask you for maximum forward speed. You want to be ready for it.
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I feel cheated, when I was working on my IR I asked my CFII about shooting an approach at a busy airport and maintaining max forward speed and he looked at me like I was dumb.

Anyway, we configured prior to the IAF, flew the whole approach at 90 knots with 10 degrees of flaps. On a 160HP C172R (approx) 2200 RPM in level flight will give you 90 knots with flaps 10. Precision approach decent was 1700RPM, non-precision we used 1500RPM.
 
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