S92 APU start
 

Can anyone enlighten me why there is a quite noticeable fuel odor in the entire cabin when you start the APU with the ECS in the HEAT position?
I'm aware of RFM Part I 2-23. Would just like to know the reason for it.

Cheers!

if you start it with the ECS heat on, i would imaging youll get fuel vapours from the unburnt fuel going through before lightup has fully taken.

cant say ive ever smelled it myself, but we dont start the apu up with the ECS running. normally start it from no power on.

have no idea what RFM says (dont do it ?)

Never noticed it because our shutdown checks require the ECS/Heat to be OFF so they should remain so until after next APU start, unless using External GPU prior to APU start but never had the need. :}

When you refer to Part 1 2-23 I assume you are referring to starting the APU with the cabin and cockpit heat off. This note refers more to the prevention of robbing bleed air from the APU during its start than to anything else. The Air Source Heat/Start switch should be in the APU position as well. AS to the vapours, I have never experienced much in the way of odor in any of the starts I did, but then again I never started with the heat ON. If one were to guess, then I would say that the bleed air that is used to heat the cockpit and cabin is being sourced from the APU meaning that the Air Source switch is either in the wrong position or is letting bleed air from the APU get by it. The bleed air would be air drawn in from around the APU and it sits just aft and between two other smelly power units, so the air is not going to be fresh initially.:} Not sure if I have answered anything, but my 2cents!

NOTE

Cockpit and Cabin heat should be off during an APU start. The heat may
be turned back on after a successful APU start.

I'm confused by the question; why start in the 'HEAT' pos when everything we have tells us to start with ECS Off. I've spent all morning reading checklists, PTM and RFM......or was that the intention!

With #1 and #2 engines off, our initial APU start is always with both ECS switches in the OFF position. Company SOP's are fairly straight forward in that regard.
I'm talking about the APU start after landing at an airport with the intention of shutting down. #1 and #2 engines are still in FLY as we taxi towards our ramp and go through the "After Landing Checklist". The last item on that list is the APU start. Sometimes it happens that we start the APU with the ECS switch in the HEAT position. SOP's and checklists are not 100% clear about this I guess. That's why this situation sometimes occurs and we then get the fuel odor in cabin and cockpit.

We start the APU on the taxi after landing with AC on no problems - never tried it in "heat".
We also used to start the APU in the air prelanding on a rig if we were going to go to idle on deck.
Ever tried it in the air with heat selected? Was the result the same?
All my 92 time is in SEA so have never used heat except during testing and then for a very short time.

Mine says

After Landing

1 Brakes..............Check
2 Heater (If shutting Down)........Off
3 APU (If shutting down)............On
4.Blah Blah

I just read this in the study guide

Following other operators’ experience, oil has been known to leak into the bleed air output from the APU and, if the heater is ON, to be transported through the heater vents in the cabin and cockpit.