Stall speeds and ASI arcs

[Ned Gravel]

Here's a picture of my ASI:

BigTex: Can you tell me the part number of your ASI? I want one appropriate to our speeds but with the true airspeed window. Sent from my iPad

[Bob_Belville]

Bob,

The Owners Manual for my C says this under Operating Limitations:

White Arc--63 to 125 MPH CAS. (Denotes speed range in which flaps may be safely lowered)

In Section VI. Performance, there's a page titled Stall Speeds, two pages before Cruise & Range. I took a picture, let's see if I can attach it on the phone.

Hank, your '70C O.M.has more detail but the same conflict, as I read it.

 

If http://en.wikipedia.org/wiki/Airspeed_indicator is correct:

 

A white band runs from V_SO to V_FE. V_SO is the stall speed with flaps extended, and V_FE is the highest speed at which flaps can be extended.

 

then Vs0 for our planes is 63 MPH based on ASI arc. What's the 57 on the chart mean?

[Bob_Belville]

BigTex: Can you tell me the part number of your ASI? I want one appropriate to our speeds but with the true airspeed window. Sent from my iPad

Ned, here's pics of mine which should work for you...

[Ned Gravel]

Thanks Bob: I appreciate the info. However, am really looking for MPH on the outer ring and the highest number should be between 200 and 220 MPH. Sent from my iPad

[Hank]

Hank, your '70C O.M.has more detail but the same conflict, as I read it.

 

If http://en.wikipedia.org/wiki/Airspeed_indicator is correct:

 

A white band runs from V_SO to V_FE. V_SO is the stall speed with flaps extended, and V_FE is the highest speed at which flaps can be extended.

 

then Vs0 for our planes is 63 MPH based on ASI arc. What's the 57 on the chart mean?

Bob, when debating the meaning of what's written in my Owners Manual, I trust its explanations much more than Wikipedia. Give me a few minutes and I can make Wikipedia say that Vs is whatever I want it to be. My Book defines the white arc different than Wikipedia, so I believe what my Book says.

Note that the white arc is defined in CAS. The page I photographed shows stall speed of 57 MPH Indicated in the landing configuration. The Airspeed Correction table does not go below 70 MPH, and that CAS varies from Indicated speeds depending upon flap and throttle position. The chart shows stall at 57 MPH.

Do you trust what Mooney said about your aircraft, or what someone wrote in Wikipedia about the meaning of the white arc?

[Hank]

P.S.--Vso for our planes is stall speed with flaps and gear extended. A minor difference of which your wiki author seems unaware.

[Hank]

P.P.S.--Stall with no flaps is 67 MPH; with full flaps it is 57 MPH. The white arc is halfway between at 63 MPH.

Coincidence?

[Bob_Belville]

found a nice short training video on airspeed indicator markings. 2-1/2 minutes.

 

 

Watch the video and then take the test:

 

http://www.aopa.org/asf/asfquiz/quizzes.cfm?sa=quizzes&quizid=130

[N6018Q]

So, 5 years later, I noticed the exact same inconsistency (at least in my mind) and as I was searching Yahoo, I came across this thread. My ASI is labeled exactly like Bob's. I was taught that if your airspeed decayed below the white arc, in a landing configuration, the plane would stall. It appears to me that this topic was dropped rather than resolved but I realize I might be missing something. @Bob_Belville, has this been resolved to your satisfaction? If so, what is your conclusion?

[N6018Q]

PS I hope that in 5 years from now, my plane looks half as nice as Bob's!

[Bob_Belville]

I've slept several times since then but my memory is that we never did come to absolute agreement. I do recall that there was a great deal of extraneous pontifications and very few (none?) authoritative explanations. I guess the best advise was to do some landing config stalls at a safe altitude and come up with Vso for your specific plane. Of course you need to take into account what the weight was during your test. 

If you read the thread you know that I was asking an academic question about ASI vs. Owner Manual. I have 2 AOAs installed which obviates the need for an airspeed #.