Airspeed Markings

[lawheelock]

A question was posed on the Yahoo site about an airspeed indicator that had a line at 100 mph and a "G" on it. I felt this was an important enough question that Stinson owners should all be aware of especially those with straight 108s like me.

Here is a copy of the question, and a copy of my answer.
Question:
On 6/3/2011 10:07 PM, n6824d wrote:
>
>
> I just purchased an original airspeed indicator for a 108-3 to replace the generic one currently installed. It has all of the correct arcs and U and N redlines. But it has a G mark at 100 mph and a P mark at 88 mph which is the flap speed. I cannot find any reference to these in the pilot's operating manual, the maintenance manual. or the Type Certificate Data Sheet. Does anyone have an answer for this? Thanks N6030M.

My answer:

You have an airspeed indicator that is marked for the original straight 108. The "G" says that you can have the flaps full down in a GLIDE (little or no power) at 100mph. This marking shows on the original operations limitation sheet for the 108. They did not put that on the airspeed for the later models, but in reality there should be no reason not to be able to use full flaps at 100mph provided you do not have much power.
This speed does not show on the current TCDS for the 108, but it is called out on the original operations limitations sheet.
I'll have to make a copy one of these days and post it.
Very few people know about this. I know the FAA people will not know about it, but it is a legal marking for the straight 108. Are the other markings correct for the 108-3? It has a higher red line than the earlier models. I have remarked airspeeds for straight 108s because they did not have the "G".
Airspeeds never have gear down speeds. The "G" is for Glide! The "P" at 88 mph is for POWER.
Larry Wheelock, N584LW, 108 with S/108-584 for 43 years, A&P, IA

[lawheelock]

Below I have attached a pdf file of the operation limitations for my airplane as found in the FAA disk.
Note that this does not say to mark the airspeed with the two flap speeds, but most likely the original TCDS specification sheet did.
The TCDS has been revised by the FAA many times and it was probably dropped without knowing what it was about.
I will attempt to post this in the files section too.
Larry Wheelock

Note: I just learned how to compress jpg files using the Windows Picture and Fax viewer. I was not able to attach the original files I made because of size.
Here I try again.

3 pages of original document Note flap speeds without power and with power

N584LW Orig Op Lim Page1 comp.jpg (41.66 KiB) Viewed 1071 times

N584LW Orig Op Lim Page 2 comp.jpg (38.82 KiB) Viewed 1071 times

N584LW Orig Op Lim Page 3 comp.jpg (37.19 KiB) Viewed 1071 times

[wmacdonald]

Larry.... Very interesting, I have a straight 108. It has the orginal airspeed indicator... no G or P markings
Thanks for the info...

Blue Skies...Walt Mac Donald & 97440

[lawheelock]

Walt,
On mine, which I am pretty sure is an original, and the few others that I have seen the markings were all on the outside of the glass. I have never seen an original with internal markings. Mine were obviously painted on with a small brush before I bought the plane in 1968. I have added them outside the glass to other straight 108s using the decal kit sold by Spruce and others. You probably don't have any internal markings, red lines, (U and N) yellow, etc? The other reason I think mine is an original the airspeed numbers are all florescent, if you shine a bright light on it they glow for a little bit. I don't have a radiation detector to see if it is a radium containing instrument.
My plane was N97584 when I got it but I changed it to N584LW which retained the serial number and added my initials.
Interestingly, the FAA later assigned N97584 to a Cessna which later crashed and there was fatalities. Then, they later again assigned it to a Cessna twin, which crashed with fatalities. If I was supersticious, I ought to be very happy I changed the number! Strangely, I can't find these in the NTSB data base now, but Have seen them previously.

Larry Wheelock