Pitot Failure use Pitch & Power for TAS?

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gtmize
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Pitot Failure use Pitch & Power for TAS?

Post by gtmize »

Years ago in a 172 my Pitot failed (bugs) on takeoff .. I just circled and landed.

I was wondering weather anyone here has suffered a failed Pitot enroute i.e. no IAS

The G1000 no help .. not sure you'll even get ground speed without IAS from Pitot
Foreflight in the cabin ... ditto

You could call tower & get it from them .. once?

I plan on taking some pitch & power (pitch, MP, RMP) settings next time I go up just in case
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AndrewM
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Re: Pitot Failure use Pitch & Power for TAS?

Post by AndrewM »

G1000 should absolutely give you Ground Speed (assuming GPS signal), and there is no reason why ForeFlight as well would not be able to provide GS as well, again assuming GPS signal.
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Re: Pitot Failure use Pitch & Power for TAS?

Post by CFIDave »

Got an iPad or iPhone with you running Foreflight? It'll give you GPS groundspeed. Based on your flying experience, you can then approximate to arrive at IAS based on your altitude and winds aloft. Such a crude estimate should be good enough to keep you out of trouble.
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Colin
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Re: Pitot Failure use Pitch & Power for TAS?

Post by Colin »

The stall vane is separate from the pitot tube and that's what I am *really* concerned about. And the groundspeed is clearly displayed even without the pitot system operating.
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Re: Pitot Failure use Pitch & Power for TAS?

Post by CharlesMc »

I had a planned flight one day about a year after getting my private license when I lost all air speed indications shortly after lifting off. My first reaction was the tap on the back up round dial to see if anything would change, nothing happened, so, called tower, explained the situation. Tower cleared me for a left 180, direct return to the end of departure runway. Worked the landing by coordinating the throttle and sight picture. While reducing power, wind noise also gave a decent relative indication of speed.

With all that said, while training for my IFR ticket, one of the members of this board sent the attached pdf file. Plug in your numbers and it becomes your template for any number of scenarios.
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Power Settings Leaning.pdf
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Re: Pitot Failure use Pitch & Power for TAS?

Post by gtmize »

Charles, thanks for your table which shows the relationship between Pitch/ Power / TAS which is what I was looking for .. It will be interesting to check these in my plane enroute. At lower speeds TAS and IAS should be close enough.

Other comments here note that G1000 provides ground speed but that's not much help unless winds are calm / zero.

And waiting on the stall horn is a bit scary unless you're on short final.

Thanks to all for your thoughts
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Re: Pitot Failure use Pitch & Power for TAS?

Post by jast »

Especially with a Diamond I would use GS+Wind estimate + gust factor from the Tower +5kt safety margin and fly 90 calculated AS over the numbers on a long runway and let it float until it settles down. If the runway is not long enough (<1500m for a DA40), rather with with 75% power to an alternate which has a long runway.
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Re: Pitot Failure use Pitch & Power for TAS?

Post by CFIDave »

CharlesMc wrote: Sun Mar 15, 2020 9:46 pmWith all that said, while training for my IFR ticket, one of the members of this board sent the attached pdf file. Plug in your numbers and it becomes your template for any number of scenarios.
I have multiple issues with the recommended pitch/power/airspeed settings in the attached pdf file.

1. You shouldn't be pitching up to 10 degrees for takeoff or missed approach. For proof, if you push the GFC700 autopilot TOGO (take off, go around) button on the left side of the throttle, the Lycoming DA40 command bars on the PFD will show a pitch angle of only 7 degrees (6 degrees on Diamond twins). The Lycoming DA40 (unlike the Austro DA40NG or Diamond twins) practically "levitates" vertically off the runway with very little pitch up needed to achieve a significant rate of climb. At 10 degrees pitch up, you also can't see over the nose very well.

2. Climb attitude should be based on Indicated (IAS), not True (TAS) airspeeds. For proof look at how the GFC700 autopilot operates when in FLC mode: it will cause the plane to climb at a fixed IAS, adjusting pitch as necessary so that the plane won't stall despite severe downdrafts. I've found this to be a lifesaver when ATC unknowingly vectors you into a convective cell while in IMC. I use 90 KIAS (rather than TAS) for cruise climbs in a Lycoming DA40.

3. I disagree with the RPMs shown for flying circuits/traffic pattern. Rather than initially reducing RPM after takeoff from 2700 to 2500, and then later to 2200, it's much easier to just reduce RPM to 2400 after reaching pattern altitude, and then bring RPM up to 2700 when abeam the numbers on downwind. Flying Threshold/Base/Final at only 2200 RPM means that you don't have full power immediately available in the event of a go-around or downdraft near the ground. For the same reason you want the RPMs set to 2700 after the FAF on instrument approaches.
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Re: Pitot Failure use Pitch & Power for TAS?

Post by AndrewM »

gtmize wrote: Mon Mar 16, 2020 8:26 am
And waiting on the stall horn is a bit scary unless you're on short final.
Just my point of view, but I think there is a lot we can "feel" in our DA40's. It is one of the many fantastic aspects that I really enjoy about these planes. In a SRxx with spring loaded controls this would be significantly more of an issue. And in the two DA40's I have owned, the stall warning horn goes off seemingly way... way before even close to a true stall. Granted, if you are close to the ground (and especially on short final with no airspeed indication) you do not want to be anywhere near stall speed or flirting with that, I am just saying that by combination of (a) feel of the aircraft (mushy controls developing? pitch / sight picture on approach), (b) knowing what power combinations you usually fly (combined with engine/wind noise), and with (c) GS indication from G1000 / ForeFlight, in the DA40 this is not an issue I would be freaking out about. Get on ground asap... yes.
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Re: Pitot Failure use Pitch & Power for TAS?

Post by gtmize »

Good BoldMethod thread - iced pitot on approach
https://www.boldmethod.com/learn-to-fly ... -approach/
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