Q400 APU and Others

[balaton]

Hi Dear Experts,

A company near me want to use a relatively low-cost aircraft in the corporate role.
Their search narrowed down to the Q400. Stage lengths from short hops to 200-400 nm, occasionally 600-700 nm. Runway lengths to a min. of 1400m. Trip time is not a factor. The possible base airport has excellent Q400 maintenace support.
Their major requirement is the absolute independnce from ground support (GPU,AIR, etc.)
In this respects I have doubts: there are widely spread rumors that the Q400 APU is extremely unreliable. Is it true? Even with newer models? Have Bombardier done something to remedy this problem?
Like to have your opinion about this and generally the q400 in the role described above.
Appreciate your help.

[flyboyike]

How many people are you planning on carrying?

[Tu.114]

I do not think the DH8 APU is unrealiable. We use it mainly to cool the cabin and only rarely to start the engines; and I have neither had to write up an APU nor flown with an unserviceable one in nearly a year despite the summer having been really hot and the APUs having gotten quite a workout.

Even with an unserviceable APU, one can be self-sufficient on the ground. Starting one engine on battery power alone and then the second one using electricity from the first one is permitted and well possible although a second startup attempt on the drained batteries may or may not be within their capabilities and it will take ages to get them loaded back to the takeoff limit of <0.1 charging current.

Caveats apply though - treat the APU well. In case of an APU-driven engine start, it is good practice to allow the APU cool a bit with the generator offline while You start the second engine using the 28VDC from the already running engine and only switch the APU off thereafter.

[flyboyike]

Sweet Mother of God, that sound almost as complicated as starting an actual Tu-114.

[Piece of Cake]

In just over 4 years of operating (3) Q400s I have only ever had an APU problem once (APU Generator wiring fault). The aircraft starts reliably also from batteries only.

I think the APUs on the smaller Dashes (-200/300) may have been where the unreliability rumours came from.