Peter wrote:
Does anyone know if Aspen/Garmin kit supports autopilot operation with airdata lost?
Garmin kit works fine (in “degraded mode” but fine) with airdata lost; it uses GPS data instead of air data. So does the latest Aspen, but only the very latest (the evolution MAX range; any older model that is not “MAX” falls on its face in the absence of air data).
On the one hand, I would expect that basic autopilot functionality works fine, that is except IAS hold mode (!) with Pitot blockage and anything to do with altitude (and speed…) with static port blockage, etc. With the addition of envelope protection in the latest autopilot, I actually wonder if the autopilot will not do “stupid stuff” like putting the plane if a very steep dive and overspeed.
Garmin is not good with this. I had an OAT failure in a G1000/GFC700 system, and that one rather insignificant failure rendered the autopilot dead except for flight director. The new GFC500 is not better, see below. It will maintain pitch attitude after loss of airspeed, but will do so with the horn blaring, and when you silence that, you will disconnect the autopilot and cannot enable it.
LOSS OF AIRSPEED DATA
(Red X through airspeed tape on the G5 or G3X display, amber AP with a red X in autopilot status box.)
NOTE
If airspeed data is lost while the autopilot is tracking airspeed, the flight director will default to
pitch mode (PIT).
1. AP DISC / TRIM INT Button ……………………………………………………………… PRESS AND RELEASE
(to cancel disconnect tone)
2. Aircraft Attitude ………………………………………………….. MAINTAIN / REGAIN AIRCRAFT CONTROL
3. Manual Elevator Trim ………………………………………………………………………………… TRIM as required
NOTE
The autopilot cannot be re-engaged. The flight director is available however IAS mode cannot
be selected. Loss of airspeed will be accompanied by a red PTRIM indication on the G5 or G3X
(if a pitch trim servo is installed)
Well, at least that makes it likely the envelope protection is also disabled, and will not do dangerous stuff.
Suddenly this thread has acquired a new dimension… Do a departure into OVC002 with the covers on and you are likely to have a wild time.
Would a pitot tube cover, leather, burn up and fall off in flight, if the pitot heat was left on?
It can certainly catch fire on the ground, with a 28V 5A heater inside it 
Do we not lift off at a specific airspeed? Would the leak of airspeed not make it obvious that something was wrong?
Peter wrote:
Same with the towbar. I once got close to doing a startup with one attached
Me too, and also due to distractions, and that I usually fly tailwheel aircraft so it slipped my mind that I’d pulled the nosewheel Grumman out by the towbar. Fortunately another pilot saw and pointed before I cranked the engine, that would have been a VERY expensive mistake.
dublinpilot wrote:
Do we not lift off at a specific airspeed? Would the leak of airspeed not make it obvious that something was wrong?
I don’t. I usually have 4-5 seconds from power on to take off and am usually focused out of the aircraft. I basically rely on sound and feel to know that the aircraft is behaving as should. I check the rest as I’m climbing up and have time.
I think the potential real concern is as noted if launching into very low imc. But then one would hopefully do an extremely thorough pre flight and catch it before going in.
I do recall though in my IMC training we did ice up the pitot at one point and it was possible to fly on pitch and power. Not that I would want to have to do this.
I will still continue to use the pitot cover, but again being high wing I hopefully would see before getting to the take off roll
“In my normal procedure, first check after setting power is “Airspeed indicator alive” and shortly after “70 percent takeoff speed”.”
I looked for airspeed. My brain rejected the instrument reading zero, and I looked for it elsewhere on panel.
Less than 30 hours on type, more than 1700 on another type with a different panel layout.
I have a new (to us) Cessna 172. On my first delivery flight home, take off…. airspeed rising, yes.., then fell to zero at about a hundred knots. Pitch and power to land, a little fast and floaty, but all good. Inspection found insect eggs inside. We now cover it religiously, there’s no way you miss it on a 172!
On my low wing RV, I have two pitots connected to redundant AHRS systems. My view: don’t bother covering, risk is non existent.
For another low wing I fly, single pitot, I don’t cover either. Again; I’m confident I can land without it, so no panic. (It’s hangared) it’s very easy to miss on a low wing, and it’s always going to happen when you do your inspection, leave pitot on due to delay an hour or two, then do a quickie inspection before flight.
A friend covers his, and has a huge ribbon attached to it that wraps over the top of the wing, so you couldn’t possibly miss it.
One very important thing: if it does block, don’t mess about poking a stick down it. Dismantle and use air compressor to blow outward. Catch the crap in your hand as it blows out!
I have neither time nor inclination to look at the panel on take-off. If I don’t have full control authority after three seconds and wheels off the ground after another three there’s something wrong, whatever the instruments might say.
I used glance down to to check fuel flow after opening the throttle, but now we can ask the nice lady in the GTN to “say fuel flow” – and keep our eyes outside.
When “contact flying”, i.e. looking out of the window, the air speed indicators (dial and G5) would tell me nothing that I don’t already know.
An exception is when towing old gliders with low aerotow Vne and perhaps when flying a lot of different aeroplanes or having only a few hundred hours in a particular aeroplane one might check the ASI from time to time, for instance before pulling up the flap lever. Even then, you can feel resistance if you’re too fast.
I certainly can’t imagine having to check a dial to know whether my aeroplane is ready to fly.
