Cessna info

[Dick Whittingham]

What is the range IAS for a Cessna 150? And does it fly nose up at this speed?

Dick

[PAJ]

Typical cruise IAS in a 152 is 95kts, TAS will be much the same at the sort of altitudes you will likely fly it at. Properly leaned, I'd say you could stretch the range to maybe 500nm. However, altitude, atmospheric consitions, wind and aircraft weight are all factors that affect max range.

[pilotmike]

IAS nearer to 70mph (around 62 kts) will give better range than the 95 kts suggested above. Of course, this speed depends upon weight.

It will adopt a significantly nose up attitude at this speed.

[Adios]

Dick,

Did you mean what is the IAS one should fly at to achieve maximum range?

[Dick Whittingham]

Adios et al,

Thanks for the replies. I am trying to answer a query on the BGS forum about range speeds, angles of attack and incidence where the questioner quoted 75kt and a nose high attitude, and as I have no experience of the type I asked here for expert advice. Is it the case that the recommended cruise IAS is higher than Vmd, the theoretical range speed? What is the recommended speed for gliding for range, e.g. after engine failure?

Dick

[pilotmike]

The optimum IAS for gliding range (ie max L/D speed) is slower than the suggested Cruise IAS, as I stated before, depending on weight.

Though I cannot speak for Cessna, the most likely reason for their recommended 'Cruise IAS' being higher would be that 'everyone wants to get there', despite the optimum range being compromised. Small changes of speed around an optimum make negligible difference, so higher speeds will be more economical of time, without being too detrimental to range.

[Dick Whittingham]

Pilot Mike,

Thank you. I have the theory, what I need are actual operating speeds from a Cessna expert. Our poster has now brought up a Cessna graph for the 172 that gives 60kt as Vmp, 75kt as Vmd and 95 - 105kt for cruise. This would make gliding for best angle 75kt, and gliding for endurance 60kt. Is this what you actually do? And what climb speed do you use?

Dick

[pilotmike]

Dick, I'm aware of your credentials on the theory. My offerings were intended more to correct the answers offered by the other contributors than to educate you on matters aerodynamic, for which there is no need!

Though I'm no Cessna expert, the suggested figures you have been given for the 172 are in the right range (depending on weight), and they fit with my offerings on the 150, where most speeds will be some 15% slower.

Some old checklist notes, circa 1980 vintage, which I have to hand suggest the following climb (clean) speeds, which I wouldn't dispute:

C150 - 75mph
C152 - 70kts
C172 - 75kts

I personally went up in a 150 yesterday, solo, with 1/3rd tanks to check for you, and the figure I suggested seemed good, though testing it is an inexact science. Later last night, not a million miles from you, I was careful to hold Vref+20 to DA at Bristol RW27, with 20018G26 1000 S001 B002, on bigger metal - a very busy approach, so not the place to test for max glide!

R'gds to you, Alex et al

[Genghis the Engineer]

So far as I know, Cessna don't publish a figure (most aircraft in this class don't), but if you've got the Cessna POH to hand, it should be reasonably easy to work it out.

From memory (I've not flown any Cessna aircraft for a couple of years I'm afraid) the POH includes tables of airspeed against fuel consumption. Divide knots (nautical miles per hour) by fuel consumption (gallons per hour) and you'll get values for nautical miles per gallon at each airspeed.

Plot a graph of that (nm/gal .v. IAS) and there should be a visible maximum - that's your best range speed in still air.

To get the value for different head/tailwind components what you need to do is recalculate by calculating (knots TAS ± tailwind component) / (gallons/hr) then plot this against knots IAS and this will give you a different graph, but the maximum will now be at the IAS value for best range for that head/tailwind component. If you got it right, the best range speed should be slightly higher against a headwind component, and slightly lower with a tailwind.

Incidentally, I'd say from slightly distant memory that 75kn is about right and would be slightly nose-high.

G

[F111D]

Here are some manuals for Cessna aircraft - from the 120-140 on up. The Cessna 150 manual is for a 1964 Patroller.

Cessna FREE Manuals (http://www.micro-tools.net/pdf/Cessna/)

You can also download a copy of the 1975 manual here

http://www.aviatickyklub.cz/files/c150L_manual.pdf

I hope this helps

[Dick Whittingham]

Thank you all very much for your help. The query has been all about range speeds and attiude, mostly starting with "how can it be true that.." and I didn't even know if it was true. During the exchanges my interrogator produced a 172 graph (www.pplkonyv.hu/download/C172-Penaud.jpg) which, as I said earlier, confirms Vmp at 60kt, Vmd at 75kt with a high nose attitude and recommended cruise at 95-105kt. He also produced another diagram from (cough) a well known school that said that Vy was Vmd.

I think we have sorted this out, but thanks again

Dick