Pitot Freezing
- Thread starter rlallen1
- Start date
GPS assist activates when airspeed goes away (to zero). This can happen when pitot freezes, but a full icing over of the pitot can also freeze in a way that traps the air pressure that's already in there. In that case, your airspeed will become unreliable, you won't see GPS assist and your attitude will be unreliable. It is because of this failure mode and our commitment to safety that we came out with our service bulletin which provides free replacement heated AOA/pitots to all of our existing customers that have ever purchased them.
I thought on a steam guage, if you will, when the pitot freezes then the current airspeed would remain the same and then the airspeed indicator becomes an altimeter and basically with altitude changes the indicated airspeed goes up or down. Are you saying that the airspeed in the skyview will go to zero instead of staying at whatever airspeed was read at the time of the freezing?.. and thus, zero indicated airspeed will turn on GPS assist.
I understand about the SB and will be sending my unit soon. thx
I understand about the SB and will be sending my unit soon. thx
jbeaver
New Member
I don't think waiting for the airspeed to go to zero is a safe approach. I wanted to test the GPS fallback myself (with an unheated pitot tube), so I found a nice icy cloud and flew through the edge of it (knowing I could make an immediate turn and be in the clear). It only took a few seconds for the airspeed and attitude to start jumping around erratically. I think there are a couple of things that you should consider changing:
1. Very erratic airspeed indications should cause the SkyView to switch to GPS assist. I was seeing 60-80 kt variations in a fraction of a second. While this might realistically happen in a thunderstorm, it's not realistic otherwise and should be ignored (especially if there are no corresponding accelerator or gyro swings).
2. It would be nice to have a way to force the SkyView to ignore the pitot and use GPS assist. Unless you can catch every edge case, there will always be situations like the one above where the pilot should be able to force the use of GPS assist.
I'm sure there is a reason for it, but why does a large airspeed change result in a large pitch change even when the accelerator and gyro don't corroborate the pitch change? Is this something you guys have considered changing? Frankly, this just seems like a bug in the algorithm.
1. Very erratic airspeed indications should cause the SkyView to switch to GPS assist. I was seeing 60-80 kt variations in a fraction of a second. While this might realistically happen in a thunderstorm, it's not realistic otherwise and should be ignored (especially if there are no corresponding accelerator or gyro swings).
2. It would be nice to have a way to force the SkyView to ignore the pitot and use GPS assist. Unless you can catch every edge case, there will always be situations like the one above where the pilot should be able to force the use of GPS assist.
I'm sure there is a reason for it, but why does a large airspeed change result in a large pitch change even when the accelerator and gyro don't corroborate the pitch change? Is this something you guys have considered changing? Frankly, this just seems like a bug in the algorithm.
DBRV10
Active Member
From memory the GPS assist kicks in with more than just zero IAS.
I have had a bug….yes a bug jammed in the tube and we had some airspeed, maybe 45 knots from memory….GPS assist came up straight away.
The full understanding of the feature would be nice to know.
I have had a bug….yes a bug jammed in the tube and we had some airspeed, maybe 45 knots from memory….GPS assist came up straight away.
The full understanding of the feature would be nice to know.
When a pitot injests or is coated with ice, it's reading might go to zero, might become completely plugged and behave like an altimeter, as you point out, or it can be partially blocked or intermittent, leading to other erratic readings, depending on the exact way that the ice is covering / sealing the pitot line. SkyView currently only changes to GPS assist when airspeed goes completely away.
We don't have specifics to discuss at this moment, but we're always researching ways to improve our attitude algorithm and our ability to deal with degraded sensors and inputs. One of the ways we've done this recently is by ensuring that our heated pitot performs they way it should all of the time, so that in a properly-equipped aircraft the chances of the pitot misreporting airspeed are as close to zero as possible.
We don't have specifics to discuss at this moment, but we're always researching ways to improve our attitude algorithm and our ability to deal with degraded sensors and inputs. One of the ways we've done this recently is by ensuring that our heated pitot performs they way it should all of the time, so that in a properly-equipped aircraft the chances of the pitot misreporting airspeed are as close to zero as possible.