Cx flyboy From Hong Kong, joined Dec 1999, 6454 posts, RR: 56 Reply 1, posted (10 years 1 month 3 weeks 6 days 21 hours ago) and read 2454 times:
A plane can indeed fail to start for a number of reasons. The fuel valves can get stuck, air valves, rotors, starter motors etc.. can all fail. Some aircraft have autostart and will manage the entire process and cease the start is a whole range of stuff happens. Most aircraft have manual starts and the pilot needs to monitor a whole range of parameters. Some failed starts require a time limit and certain procedures for a restart. Different companies and different aircraft types have differenct procedures and numbers of restarts allowed. Something like a stuck valve may mean that they cannot try a restart until the problem is fixed.
To get the plane going again, really depends on the problem to begin with. It may require a quick fix only, or it may ground the aircraft and a new aircraft has to be found. Really depends on the situation.
S.p.a.s. From Liechtenstein, joined Mar 2001, 957 posts, RR: 3 Reply 2, posted (10 years 1 month 3 weeks 6 days 18 hours ago) and read 2429 times:
I once heard a tale (never was able to confirm its veracity) but according to it soon Swissair started ops to Moscow with A320s, during one nice winter day air pressure was very low and temperature also and this combination was below the valid values that the computer had stored, specially for air pressure..
So, still according the tale, as the start is computer controlled, the black box "didn't let" the engines to be switched on, as the pressure would be "impossible" It was a minor software glitch...
As a result, a Crossair MD83 was flown to MOW to get the stranded passengers, until a revision on the software was loaded into the Bus.
Might be true... might be not... but anyhow makes a nice pilots pub tale
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 36 Reply 3, posted (10 years 1 month 3 weeks 6 days 10 hours ago) and read 2318 times:
The most common reason I've seen for an engine not starting (provided the engine is motoring) is an inop ignition system. Whether the excitor box, ignitor, ignitor lead or wiring is at fault is another story.
And of course if the engine doesn't even motor then the start valve or any wiring or switches leading up to it are probably at fault.
Cdfmxtech From United States of America, joined Jul 2000, 1338 posts, RR: 28 Reply 6, posted (10 years 1 month 3 weeks 5 days 9 hours ago) and read 2112 times:
I think it must be one of those myths, because if it was true how would you manage an in-flt start?
Simple just enable an Air/mode inhibit. From what I hear, Airbus is bizarre enough to impliment something like that in their systems. It seems like they are always trying to add a "wow" factor to their aircraft and systems.
Wow, that's a neat trick.
B747skipper From , joined Dec 1969, posts, RR: Reply 7, posted (10 years 1 month 3 weeks 5 days 4 hours ago) and read 2090 times:
Say - an engine does not start... OK, guys - let's move the switch to "GND START"...
"Nothing happens here"... well, could be start relay (start valve)...
Verify the CB for start valve relay... cycle it...
Well, maybe start valve opened, but "NO AIR" goes to engine starter...
Indication: engine rotor (most engines = no rotation N2)...
Verify air source - often it is an APU... is there air pressure...
I that valve open or not...
Is there is air pressure? Send mechanic to open the valve manually on the engine...
Say, that N2 shows rotation...
OK, with put the "fuel ON"... a few seconds later... still no EGT, and no FF...
No FF - fuel flow... well, is the fuel going to the engine...?
If there is FF indication... well, then, it is IGNITION which is the problem...
Problems to start an engine... simple if you analyse the problem...
Obviously, "them planes" designed by the Toulouse rocket scientists must be beyond my IQ...
That is the reason I stay on the 747 until retirement...
Thereafter I will fly my L-21...
So simple... with a start and L/R magnetos, and a manual fuel valve selector.
KISS = Keep It Simple, Stupid...!
Liamksa From Australia, joined Oct 2001, 308 posts, RR: 0 Reply 8, posted (10 years 1 month 3 weeks 5 days 3 hours ago) and read 2061 times:
If there is FF indication... well, then, it is IGNITION which is the problem...
Is this where wet starts could come into play? If the igniters failed to fire for the first few seconds whilst fuel was flowing, and then they magically did for some reason, would you have a wet start on you hands?
To avoid this situation would you motor then engine over (ie: not using igniters) to clear unburnt fuel?
ChallengerDan From Canada, joined Sep 2003, 167 posts, RR: 0 Reply 9, posted (10 years 1 month 3 weeks 5 days 1 hour ago) and read 2042 times:
Not a wet start, but a hot start! after a few seconds, if you don't have light-up, you usually dry-motor the engine (cranking it without putting any fuel) for a couple seconds to get the fuel out of the combustor. If you don't do this, or like you mentionned the igniters would suddenly come back on line, you would experience a sudden rise in ITT(temperature of the hot gases going to the turbine) that could potentially cause damage to the engine.
if your flight goes MX in YUL, I might be called to fix it!
B747skipper From , joined Dec 1969, posts, RR: Reply 10, posted (10 years 1 month 3 weeks 5 days ago) and read 2038 times:
A bit of education to a few of you here...
About "hot starts"...
With many hot starts (excessive fuel)...
Procedure calls to pull the "fire handle" which has a definite drawback.
The fire handle "kills the air" to the starter... thereby stops engine rotation...
Yet - the best, in case of hot starts is - "motor the engine"...
And "blow out" the tail pipe fire and excess fuel.
Most airplanes - the fire handles interrupts -
Fuel to that engine (good thing) -
Hydraulic pump (at that stage, not critical) -
Trips the generator of that engine (at that stage, not critical either) -
Shuts bleed air valves to/from engine - who cares -
The fire is not in the compressor... it is in the tail pipe...
Rotating the engine (with starter) is the best, yet...
I wish the fire handles were designed to still permit rotation by the starter.
Liamksa From Australia, joined Oct 2001, 308 posts, RR: 0 Reply 11, posted (10 years 1 month 3 weeks 4 days 6 hours ago) and read 1933 times:
Ah OK Skipper, so the fire handle kills the starter air and fuel supply (and the rest). I see that ideally you would keep it turning over to clear the excess fuel or tailpipe fire, so how do you "motor the engine" on a modern aircraft? Fuel cut off, igniters off, then engine start?
Air2gxs From , joined Dec 1969, posts, RR: Reply 12, posted (10 years 1 month 3 weeks 4 days 2 hours ago) and read 1912 times:
I can tell you on "modern" Boeings (57/67) that you just move the start switch to ground and supply air. As long as you ahve a good airsource, you'll get at least 20% N2, probably closer to 28%. Don't throw in the fuel and your dry motoring.
Watch starter duty cycle or you'll trash the starter. The actual time eludes me at the moment. It varies from engine to engine anyway.
B747skipper From , joined Dec 1969, posts, RR: Reply 13, posted (10 years 1 month 3 weeks 4 days 1 hour ago) and read 1907 times:
The problem is that the "fire handle" kills all bleed air sources IN and OUT of the engine... so the starter does not get any air... and cannot rotate the engine...
In my opinion, the start valve should be left open to permit to motor engines, to blow excess fuel when the fire handle has been pulled for a tailpipe fire.
I wish design engineers had permitted that feature to be kept on start valves...
All pilots and instructors in aviation have that same opinion.
Air2gxs From , joined Dec 1969, posts, RR: Reply 14, posted (10 years 1 month 3 weeks 4 days ago) and read 1902 times:
I just went through our hung/hot start checklist here and couldn't find any reference to pulling the fire handle. I'm not sure what our AOM says about it, but from the maintenance put of view the only time we pull a fire handle is when the bell is ringing. What airline or fleet type?
Vc10 From United Kingdom, joined Nov 2001, 1395 posts, RR: 16 Reply 17, posted (10 years 1 month 3 weeks 3 days 16 hours ago) and read 1838 times:
Back in the 1960's a VC-10 aircraft in the wilds of Africa could not open it's start valve on one of it's four engines, so it off loaded it's Passengers and cabin Crew and took off on the other 3 engines. Once in flight it started it's offending engine using the in flight procedure, then landed again and took it's passengers on board and proceeded to it destination only slightly late.
Would not suggest anybody try it these days as companies are not the same now , and some modern day passengers would probably sue
B747skipper From , joined Dec 1969, posts, RR: Reply 19, posted (10 years 1 month 3 weeks 3 days 13 hours ago) and read 1805 times:
Hot start procedure ("impending hot start") is just calling to shut the fuel, and continue motoring the engine down to an acceptable EGT... Probably explained it wrong here. Some hot starts (excess fuel, late ignition) have degenerated in a bad combustion stage/tail pipe fire in which the crew aborted the start and properly call for engine fire check list procedures...
Fdfmxtech is correct, you can still motor the engine with fire handle pulled, if I made the contrary statement, it was my mistake... Fire handle only shuts bleed air valves, air exiting the compressor stages...
Air2gxs From , joined Dec 1969, posts, RR: Reply 20, posted (10 years 1 month 3 weeks 3 days 2 hours ago) and read 1746 times:
Don't back off so quick. The fire handlw WILL close the pylon valve on a jumbo, thus isolating the engine from the aircraft pneumatic system.
Had a real interesting and exciting engine start once at JFK:
Ground air and electrics hooked up and starting #4.
Ground electrics trip off at about 35% N2 (light up has occured).
No electrics w/air on: pack valves open robbing air from engine.
Engine hangs and EGT climbs rapidily, almost dizzyingly (sp?).
Flight crew pulls handle and blows bottle, guess what?, no help.
We got lucky, established ground power and quick thinking engineer put in fire handle and re-engaged (crash) starter and motored until cool.
1 borescope, 2 fire bottles and a starter change later the aircraft departed.
B747skipper From , joined Dec 1969, posts, RR: Reply 21, posted (10 years 1 month 3 weeks 2 days 15 hours ago) and read 1715 times:
Correct on the 747 for the pylon valve...
We were discussing other airplanes as well, and in general, as mentioned by Cdfmxtech, other airplanes permit using the air starter despite fire handle...
I did not want to enter in a controversy here, but with my airline, if we have a tailpipe fire, we will motor the engine rather than pulling a fire handle. All we do is shut the fuel (as in "hot start") then continue motor the engine. Pulling the fire handle and use the pylon fire extinguishers would not do anything to the fire in the tailpipe... I think this airline had an incident 15 years ago, and they damaged an engine by fire following a "fire handle" being pulled for a tailpipe fire...
N243NW From United States of America, joined Jul 2003, 1575 posts, RR: 21 Reply 23, posted (10 years 1 month 3 weeks 1 day 5 hours ago) and read 1617 times:
I suppose this question is directed toward jet aircraft, but...
You haven't truly heard a backfire until you've heard one from a 2000 horsepower Pratt radial in a Corsair (at the 2003 OSH airshow). After one failed start, it backfired a few more times and taxied (noisily) away to the runway. Wow!