Hi,
Originally posted by sensor_validation
(#1385)
The A300 FCOM mentions 28VDC and 320W, but the actual power deliverable will not be constant.
I wouldnīt like to design one with much more than this ~12+ Amps. A temp. feedback is easy to implement and has benefits.
The probe heaters are made out of resistance wire, the actual resistance changes with temperature, so monitoring the current gives an indication of the heater coil temperature.
We donīt know if this parameter is used for the pwr modulation.
In other applications such as process industries handling flammable materials self limiting heat tracing tapes are used exploiting this effect.
n/c
For what power - consider a bench soldering iron - 12W can be used without any control to limit tip to about 200degC. 60W irons need temperature control - can only use higher power when soldering big things. Instant heat guns 100W will heat tip to red-heat in a few seconds. I'm sure you don't want the pitot tube more than 60degC on the ground, but its very important that you can check the heating - design case for heating and drain holes will be take-off clinb in bad weather.
Typical pwr modulation steps could be:
1) "Idle" (your 60 deg)
2) Normal, letīs say the current max power used today (approx. 300W)
3) Max, when a temp. sensor (TAT?) "inform" itīs required or JUST AFTER UAS is detected. (feedback from temp. sensor return pwr to Normal step)
4) A manual mode (time limited) for Max activation (feedback from temp. sensor return pwr to Normal step)
Note. This approach TOGETHER the "use of IR data" during short term (detected) UAS could IMHO reduce the UAS cases (water, ice, etc. related)
I am assuming the UAS cases could be less frequent using higher power.
How much more? But this requires replacement by new Pitots with Max pwr handling capability. Or even with pressure transducer separated.
Obs. The use of higher voltage: 115V in order (if heater MTBF is preserved) to apply more than 28V (by transformer) or by "inverting" 28V to letīs say, 50% could led to the use "the same" Pitots. Commenting on that iīm just "optimizing" overall costs. But this is questionable by many reasons.
The other option is to use the
Laser "pitots" when (if ever) available.
A Patent filed by EADS less than 6 months after loss of AF447.