Bleeds OFF T/O after de-icing

[upgrade]

Anyone know of any operations manual(manufacturer or operator) that prohibits or recommends against such a procedure due to possible ingestion of de-icing fluid in the APU.Aircraft concerned is 737-400. Scenario-APU shut down during de-icing,packs and bleeds off.APU re-started after de-icing.Bleeds off T/O results in air-conditioning smoke in flt deck/cabin...any help greatly appreciated

[dallas dude]

Upgrade

Sorry, I don't fly a 737 but I can tell you it's common to turn off packs, engine and apu bleeds whilst being squirted with glycol etc.

Usually this "silence" would continue for about a minute after the de-icing was finished to ensure the fluid had dissipated around the engine cowls.

Typically, the taxi checklist (and control surface check) is repeated again and this is where the bleeds are usually returned to their desired operational position.

The de-icer's do their level best not to spray in to the engines but sometimes the wind/conditions make this an impossibility.

Hope this helps.

Cheers,dd.

[static]

Upgrade,
I fly 737. There`s nothing in our books prohibiting us making a no bleeds T/O after de-icing. However, if we make a no-bleeds T/O, we do use the engine bleed with packs during taxi. We switch off the eng. bleed shortly before the T/O roll. Maybe there`s a difference with your books.

[upgrade]

Thanks for your comments,dallas dude and static.Very helpful

[m&v]

On the 320,its emphasized that the 'engine'anti-ice selected on first to 'purge'the system of fluid residue,prior to selecting packs on.Could this work for you?? cheers..

[Spearing Britney]

Interesting M&V I've never heard of that before and I can't find it in my FCOM but I can't think of any reason why it wouldn't work - is it a company thing or could you give me a reference to it?

[Ignition Override]

Dallas: Are you on the MD-80? If you are on the silver birds, I know a few guys there.

After we deice, there is no delay before putting the outflow valve back to auto and switching on both packs etc, as on the 757. If we could just avoid MSP and DTW this winter...

[CaptainSandL]

Upgrade,

Our company does not insist (or even recommend) not doing a bleeds off take-off after de-icing. Usually the associated contaminated corrections will make a bleeds off take-off a necessity.

If your concern is fumes in the cabin, then the (737) manual says:

“If de-icing fluid has been used in an engine inlet, do not use bleed air for air conditioning from that engine until all fluid has been cleared from the engine.”

So why not start the APU up after the de-icing, keep its bleed air off, let it run for a while to get rid of the fluid and then use the APU bleed air.

If your concern is for the APU, then the same book says:

“With APU operating, ingestion of de-icing fluid will cause objectionable fumes and odors to enter the airplane. This may also cause erratic operation or damage to the APU.”

So we can never safely clear the ingested fluid without running and possibly damaging the APU – life is a bitch !

If you really need the engine bleeds off, and want to avoid fumes and a damaged APU, I think strictly speaking you are faced with an unpressurised take-off.

S & L

[upgrade]

Captain Sandl,
Thanks for that info.In this instance,I believe the problem was twofold:
i)a/c was over de-iced(according to the line
engineer who witnessed the procedure)..
ii)APU/engine bleeds turned ON too soon after de-icing
Unpressurized takeoff never considered but perhaps this was the answer.