ram rise, ram recovery

[newcrew]

ram rise, ram recovery

am i correct in saying the above too things are not the same

do turboprops with tas=270 have either,neither or one of the above (i would have thought ram rise but not ram recovery?)

thanks

[oxford blue]

You always get ram rise because of kinetic or adiabatic heating of your total air temperature probe.

There is a more complicated formula based on Mach No, if you're interested, but in practical simple pilot terms, the ram rise is (TAS / 100) squared.

So, with a TAS of 270, the ram rise would be about 2.7 squared, or about 7 degrees celsius. In other words, the SAT is about 7 degrees colder than the (indicated) TAT.

However, the temperature-gathering efficiency of your probe will be less than 100%. You always lose some of the measured heat through inefficiencies of measurement.

The percentage of the measured ram rise to the theoretical lossless ram rise is the recovery factor. But on most modern probes it is of the order of 90% or more, so it can usually be discounted. It usually makes less than a degree or two to the measurement, which is close enough for all practical purposes.

[newcrew]

thanks for the info re temp probe i was taking about turboprop and turbofan engines though

my mistake

[blackmail]

hello every one,

formula is: Tt=TAT=T[1 + r.0,2M]
with T= outside air temperature in Kelvin = °C+273
Tt=total air temp also in Kelvin
M=machnumber
r=recovery factor= approx 1[rosemount temp probe] for this exercise(0.8=actually the more correct figure).

in practise for the ram rise, you multiply yr machnr x 3 & add to TAT reading(in °C) & endresult = negative.
eg, M=0.7 & TAT= - 20°C, so 3x7=21+20=41 & OAT=-41°C(with 21°C equalling the ram rise).

jeppesen plastic cr computers allow some calculations cfr ram rise & recovery factors.

[Cardinal]

To answer newcrew's question, yes and yes. ram rise has been discussed. Ram recovery is very evident. A PT6 example: Set torque at 3750ft/lbs at 160 KIAS, allow the aircraft to accelerate to 220 KIAS and you'll note nearly 4000ft/lbs, at the same N1. Then turn the inertial separators on and watch the power disappear again.