Me too, just bought a '66E

[yvesg]

Thanks Mike. Appreciated. Yves.

[Marauder]

Ugh. Does that mean it will also display the wind in mph? That IAS at the airspeed indicator is in the same unit as the POH and the main indicator is makes sense, actually the other way would be dangerous. However, TAS, GS (so why don't they insist you use mph on your GNS430 as well??) and certainly wind makes none at all! For me that would be a total show stopper to actually buying one and I am close to that decision. Actually, with your ASI being in KTS primary, so should the Aspen be. Period. Everything else is dangerous. Need to talk to my avionic shop about it. I wonder if they refuse the purchase if I make the condition that the unit is in kts. My airspeed indicator is both as well, but mph primary. Actually, I do wonder if the Swiss FOCA would accept a converted POH ammendment with all values converted to KT in addition to mph. I've done that a long time ago for the cruise tables and could do the other few pages indicated in about 2-3 hours flat. I have a feeling, if it's done properly it might get accepted. MPH should be finally eliminated from POH's as well as from airplanes. Like QFE it is something which can lead to pretty nasty errors. And after all it was only ever used to please the marketing folks to brag about higher airspeed.

I flew for years in the mixed model you spoke about. I used knots for flight planning and mph for the v and reference speeds for the plane. It was confusing. I was fortunate that my manual is printed in both and I was able to move everything over to knots to simplify the math.

[adrian]

The Aspen in my M20E is calibrated in knots. The avionics technician was initially reluctant (although he worked for my company), but I convinced him that the old analogue ASI which displays mph and kt was the primary, and that as there was no requirement for a backup display (the Aspen) it didn't matter what units I used.

The only advantage of mph is that the gear and flap speeds don't seem quite so depressingly low!

[Bob_Belville]

The Aspen in my M20E is calibrated in knots. The avionics technician was initially reluctant (although he worked for my company), but I convinced him that the old analogue ASI which displays mph and kt was the primary, and that as there was no requirement for a backup display (the Aspen) it didn't matter what units I used.

The only advantage of mph is that the gear and flap speeds don't seem quite so depressingly low!

I like and agree with your logic though I could not get Aspen or the avionics shop to buy it. Did he do the install so that you can turn the air speed tape off and on? Might come in handy. Prying eyes... (FWIW, I will not be posting any more pics of my Aspen.   

[adrian]

Not sure - I'll check next time I fly. The change from mph to knots didn't need any involvement from Aspen - the avionics technician did that after installation in the aircraft.

[rob]

Your logic is flawed, I believe, as the Aspen STC requires that it becomes the primary instrument. Or something like that. I tried similar logic in trying to talk a shop into an electric AI without a battery backup, saying that the Aspen would be the secondary. They didn't buy it.

[Bob_Belville]

Your logic is flawed, I believe, as the Aspen STC requires that it becomes the primary instrument. Or something like that. I tried similar logic in trying to talk a shop into an electric AI without a battery backup, saying that the Aspen would be the secondary. They didn't buy it.

There is a flow chart, Fig 10.13, in the Aspen installation manual that branches thus:

 

Is Altimeter and Airspeed Indicator still in Basis "T" configuration?

If no, Tapes must be configured to LOCK ON

If yes, Tapes can be configured to UNLOCKED or any other customer preference

 

The "tapes" in question are the ASI and Altimeter

[rob]

Aah, I forgot about that. Maybe then with the ASI you are able to claim its secondary and change it up....

[Bob_Belville]

Apology accepted.