ATR 42 questions
 

Have a few questions for ATR pilots.

1. What is the RNP for ATR42?
2. The ceiling of ATR42 in 25,000'. Why is that so? Can it climb any higher? Say in Ferry operations?
3.What is the technique to recover from a dutch roll?

Many thanks!!!

1. Ours are RNP5. Dunno about the newest airframes from Touluse
2. 42-500 has no problem to climb FL250. The 72 struggles but it's possible if low SAT/light a/c. Heard of ferry flights up to FL300, but never tried and doubt it's legal
3. Switch the Yaw damper back on? I don't think there's any special technique...

Cheers!
Stuck

Item 2.

I suspect that the 25000ft limit is due to not having a drop out oxygen system.
Same as Dash8 Q400. Certified ceiling is 27000ft with drop out oxygen but Flybe's are certified to 25000ft to save money and weight.

hope this helps.

Re Item 2:

Both comments above are correct - it is solely due to the lack of the dropdown O2 system. It is legal to ferry or operate the ATR above FL250 if you have sufficient supplementary O2 onboard for everyone concerned, which is why it is common for them to be ferried above FL250.

Re the dutch roll - it's been a very long time since I flew it, but....from memory, it is almost a non-event on the ATR and only done in the simulator to tick a box in the FAA-required syllabus. Recovery was to make a gentle aileron input towards the down-going wing, then when the aileron had 'caught-up' with the roll, make a gentle opposite correction to wings level. Then follow-up with gentle rudder input to re-centre the ball, retrim, re-engage yaw damper. Most simulators react badly to agressive rudder inputs anyway, so not a good idea to tramp on the pedals.
But, as I said a long time ago, so this may not be the current thinking.
RNP approval will depend on the individual installation. Some were built to an ETOPS standard. (90 minutes, I think?)
FL250 is a certification standard limit if you don't have drop-out oxygen and applies to several other turboprops, most of which are capable of flying higher, just not 'legal' to do so. The builders then tend to arrange the pressurization capability around this, so the cabin will be at or just below 8000ft at FL 250.
The AFM will state the maximum approved operational altitude.

RNP is a function of where you want to fly, not what you are flying in.