A320 fuel/oil smell just after startup

[aviatordom]

Hi all,

On a few weeks ago i was on an EZY "Bus" to Malaga from Stansted. Just after startup i noticed a strange fuel/oil smell which only lasted for about 3-5 seconds but smelt pretty good!

On the return flight i could again, right after startup smell something which smelt like fuel/oil

Now, i only know the basics about flying and i'm not very technical with all the systems, etc....

So, could anyone please explain to me what this smell was?

[Dream Land]

While the aircraft is being pushed back wards, the APU in the tail is supplying air to the air conditioning system, exhaust from the starting engines is ingested by the APU.

[aviatordom]

Thanks for the quick reply!

[Dream Land]

Having a re-think, usually the smelly fumes noticed while being pushed back, so the exhaust fumes must be from the APU exhaust, others will correct me if I'm wrong. :confused:

[F4F]

Dream Land first theory was the better one :)

live 2 fly 2 live

[ground_star]

Dont EZY only fly 319's or have they gone up in the world?

[student88]

Usually that happens if the wind is blowing up the chuff of the engine. Exhaust smells are re-ingested into the engine and circulated around the cabin through the air con.

Dont EZY only fly 319's or have they gone up in the world?
Nah, it's still the Routemasters ;O)

S88:ok:

[aviatordom]

Very interesting, thanks!

[bishop99]

Ive noticed it quite often during push and start.

Is it potentially toxic (especially after watching the panorama episode with the Bae 146 and B757)??

Regards to all,

B99

[aviatordom]

I thought that at first, but then i thought before posting "Surely, there couldn't be a problem like this on what is the world's most popular commercial airliner, someone must of noticed it before?"

I would be very interested to know if this "smell" is toxic. If so, could it be a flaw with the A320, some A320's with worn parts, the CFM-5B engine with a flaw or a worn part on the CFM-5B engine, etc....?

Should i report this to EZY just in-case?

[compressor stall]

From the 319 FCOM...

"Turn APU BLEED OFF just after Engine Start to avoid ingesting engine exhaust gases."

Airbus certainly know about it. :cool:

[Dream Land]

I notice a big whiff during the first engine start while pushing back, turning off the APU bleed is not an option.

[Mäx Reverse]

We fly A319s/A320s with CFM-Engines and A321s with IAEs.

I regularly observe this exhaust-like smell during startup, usually during the first engine start (no.2 engine), but only on the CFM-powered ships.

Exhaust re-ingestion and distriibution via the air-condition sounds good, unfortunately the packs are switched off automatically before engine-start, so this explanation doesn't stand further examination.

Any orher guesses?

RGDS Max

[Dream Land]

Exhaust re-ingestion and distriibution via the air-condition sounds good, unfortunately the packs are switched off automatically before engine-start, so this explanation doesn't stand further examinationGood call, the plot thickens. :}

[OutOfRunWay]

Yes, but on the Ground the valves open again after a 30 Second Delay. In light wind conditions this is early enough for some of the engine start stink still to be around.

regards, OORW

[Wirelock]

i think i certain amount of the fumes in the cabin can be caused before starting engines with a tailwind. the reason.? because fumes from the apu exhaust are re-ingested by the apu. the close proximity of the apu exhaust and air inlet makes this a very common occurence.

[Jimmy Do Little]

It's the oil smell that removes the APU and Packs from contention in this bout. The oil (and fuel) smell after startup is the first indication of a worn Number 3 Engine Bearing Rear Seal.

Other possibliities include...

Oil contamination at HPC stages 3 and 4, or the 7th stage Bleed Valve.

When any of these happen, the oil smell will be noticed during startup, and to a lessor degree when the engine is operated at Idle (for example, during decent).

Other than the smell, this is not a great concern INITIALLY- except to the airline accountant who can expect to be paying for the removal of the engine in order to repair the problem.

[Dan Winterland]

Oils smells from the APU can also come from people not following the securing checklist properly. The batteries shoud only be switched off when the APU door is closed. Do it before and oil from the APU can be sucked into the ducting (not sure why) giving an oil smell when the APU bleed is on. This is of some concern as engine oil fumes are toxic.

[Jimmy Do Little]

Reference please? Mine is the Airbus AMM and TSM (Air maintenance and trouble-shooting manuals)

[Wirelock]

the amount of oil consumed by a320 APU is very little, unless there is a problem in the apu. normally the apu is only used on average 30 minutes per apu cycle. the apu would only be running in flight if there was a problem with engine bleed on 1 engine. for this reason it is unlikley that the fumes are toxic coming into the cabin from the apu.

[CONCOMBRE]

Anyway,

I experience that sometime :E; after start up sequence, when:
eng mode selector and APU bleed aren't turned off, fast enough :zzz:.

[Flexable]

Similar to farting downwind...

Following is a more technical explanation...:O

YouTube - Captain Bruce goes Cropdusting (http://www.youtube.com/watch?v=zYxrzmb_gdA&feature=relat) ed

[j_davey]

Dont EZY only fly 319's or have they gone up in the world?

319/320/321 now, way way up in the world! they acquired ex GB airways aircraft afaik.

john.

[hedgehog-in-fog]

Suppose sometimes some air still is sonsumed by APU BLEED duct during eng start because of valves are not completely closed. That's why there's smell.

[Funnel Cloud]

I thought that at first, but then i thought before posting "Surely, there couldn't be a problem like this on what is the world's most popular commercial airliner,

Isn't that the B737?


Sorry....couldn't resist. :rolleyes:

[Dan Winterland]

"Oils smells from the APU can also come from people not following the securing checklist properly. The batteries shoud only be switched off when the APU door is closed. Do it before and oil from the APU can be sucked into the ducting (not sure why) giving an oil smell when the APU bleed is on. This is of some concern as engine oil fumes are toxic."

"Reference please? Mine is the Airbus AMM and TSM (Air maintenance and trouble-shooting manuals)"


FCOM 3.03.26 p1. Securing the aircraft:

BAT 1 and 2........................................................... .....OFF
Wait until the APU flap is fully closed (about 2 minutes after APU AVAIL light goes out) before switching off the batteries. Switching the batteries off before the PU flap is closed may cause smoke in the cabin during the next flight.

[dream747]

From the 319 FCOM...

"Turn APU BLEED OFF just after Engine Start to avoid ingesting engine exhaust gases."


After engine start the bleed air supplied to the cabin for air conditioning and pressurising will come from the engines and no longer from the APU. How will keeping the APU bleed air on ingest fumes into the cabin?

[vapilot2004]

With bleed valves shut and whether packs are on or off, the piping will still retain a little of the contaminated air and send it through when the valves are reopened after start.

I agree that tailwind components are the most likely cause of the offending ingestion A surge from the fiery end has been known to travel upstream to the HP bleed stages and beyond.

Blah blah blah.....
Before jet engines were trusted with supplying clean cabin air, turbo-compressors were used for cabin air back in the days of the 707. The arrangement was a turbine fed by engine bleed air connected to a compressor with its own fresh air intake for the cabin.

[Checkboard]

What goes around, comes around! :bored:

Now that turbine engines are no longer trusted to supply clean air, the 787 has been designed with electric compressors for pressurisation. In fact the only bleed system on board is engine cowl heat. Wing heat and start are electric also. :8

[IFIX]

@Dream747,

I'm not familiar with the engines installed on the Airbus 320 series, so correct me if I am wrong.

The engines when running at idle supply less pressure than an APU.
Leaving the APU bleed on ,while engines on, will only keep the check-valves in the engine bleed supply ducting closed.
The apu will still be suplying all the air into the packs.

It's why an engine cross bleed start requires adding power on the engine already running to obtain sufficient start pressure.

IFIX

[Wirelock]

no correction needed....:ok:

[gearpins]

even though the packs are "off" during start, there is still the hot air valve through which the smell can reach the cabin...:)

[dream747]

I notice that the cabin lights flicker after one of the engines begins to spool up during start-up which I suppose the reason for this being the engines powering the aircraft systems, taking over from the APU. What kind of systems govern such a transfer of power from different sources? I can imagine it must be pretty efficient to immediately transfer power to the APU once the pilots cut off all the engines at the gate.

Correct me if I am wrong, the power for these supplies from the engines will only be available when the gearboxes in that particular engine are driven at a sufficient speed. I suppose different engines drive gearboxes of different purposes and usage, can they be driven by any other means should a particular engine fail?

And what do these gearboxes drive? Alternators and such?

Many thanks guys!

[vapilot2004]

The flickering you see during start up and shut down is the load being switched from engine to APU generators and vise-a-versa. Power is usually switched at the gate to ground power so the APU can also be shut down.

The engine generators will automatically drop off line as they slow down and the output falls out of spec. The arrangement on most aircraft has the AC power switched to the next available source automatically.

Windmilling engines can supply hydraulic and electrical needs depending on airspeed and type.