Originally Posted by
Pilot DAR
Interesting observation. Indeed, referring to the POH for the 1966 150, Vx at sea level is presented as 52MPH, as you note, 1968 150 is 57 MPH, and the 1974 150 is 70 MPH. The only difference which may be found between these airplanes which could affect performance would be the pitch of the prop, which is not stated. That said, the pitch of the prop shouldn't have much affect on climb speed. The engines, gross weights and wings are the same for all of these years, and the differences in landing gear and cabin width shouldn't affect climb speed. And, the certification basis for each of the planes is the same, so same climb criteria.
If I had to guess, I'd say that Cessna began to be liability aware. Super slow climbs will give a steeper gradient, though have a much lesser margin of safety. Remember that if you're climbing at an airpseed slower than glides speed, an engine failure will likely result in a crash, as entering a glide and flare to land may not be possible. I have a STOL kit on my 1975 150, and I would never climb at a speed slower than the fast '60's, unless it were life or death!
I note that in Caravan flight testing I did years back, I found that Cessna had prescribed a deliberately fast after takeoff and VX. I got a better climb angle at a slower yet speed, but it was terrifying in the case of an engine failure (which was what I was to test).
As for the 150, if you need to articulate this to an examiner for a flight test, state the speeds in the POH, and then suggest that as the later models are presented with faster speeds, that's what you'd like to do, just to be safe. A climb at 52 MPH in a 150 is not worth the risk!
Yes i agree, I fly in the U.K from a relatively short strip and I use 60 knots/70 Mph as my usual climb figure, or 65 at the absolute minimum.