Turboprop shutdowns
 

Why do SAAB340, Beech 1900, Dash 8 etc, ie turboprops take so long to shut down once they park on the bay. Jets stop on blocks and almost imediatly shut down yet the propjets sometimes idle for 30 secs.. .. .I think it has something do do with having to shut down various systems, electrical, pnuematic, hydraulic etc, but would like a definitaive answer.

Saab 340 manual recommends 2 minutes at idle power before engine shut down so this could be your primary reason (if the taxi in is short). Otherwise delays occur due to the need to shut down certain systems (packs, electrics, etc) and more importantly the props have to be taken out of Beta mode and into feather before selecting fuel off.

On the ATR, wiht PW120´s series engines, it is reccomended 1 minute minimum of cooling time, so the ITT will be for the next start at or below 200 ºC.. .. .On the taxi-in the tasks are for reconfiguring the systems for the next flight, and besides anti-ice, there is no need to shut down, hydraulic, pneumatic nor electrical, they shut down by themselves, actually yous just sit and watch!. .. .So the real reason is for cooling the engines, they are encased and they run hot (600ºC)

I guess some of us is waiting for the GPU to be connected as well.

I think the Dash 8 ops require 30s for oil scavenging. I could be wrong but it's been a while since I have been near one.

Oz,. .. .Most, if not all, turbines require a 1 to 2 minute warm down, to allow temps to stabilise prior to shutdown. This is usually achieved during taxi in, often there will be a NL or N2 limit. In other words, if you exceed x% NL/N2 during taxi, the warm down period starts again.. .. .In the case of time on blocks prior to shut down for the DH8, the prop is hydraulically controled, for fine, coarse and feather. Consequently it uses a signifficant amount of engine oil for its pitch control.. .. .deHavilland recommend a minimum of 30 seconds idle after the prop has featherd, to allow the oil scavenge system to return the oil to the sump. Failure to follow this procedure will result in an incorrect oil quantity reading in the sight glass.. .. .Can't answer for SAAB or Beech.

Interesting claret always wondered why the Dash 8 taxies in, then feathers and sits for a while before shutting down, most of the others appear to just feather then shut down straight away..very interesting you learn something new everyday!

In that warm part of the world I was flying the 1900, we would shut down Number 1 on stand. Therefore N 2 could keep providing the power required to run the air cond without using the battery. That was done until the Fwd door was opened by ground staffs, allowing some air inside the cabin and the Pax out. Then without any mercy we could kill N 2 !!...