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Posted: 9/13/2005 4:10:42 PM EDT
Ok, got a question...is this a typical maintenance issue, a once in a while thing, or a bad thing that never happens and the plane shouldnt have taken off....
I boarded the aircraft and took my seat which was in the back of the plane. The air coming out of the overhead jets was hot - not the typical cool air that blows out. I didnt think much of that until the scheduled departure time came and went and we had not even taxied out of the spot yet. Then someone comes over the intercom and says that there is a part on the plane that is responsible for the hot air coming out of the vents which is also responsible for supplying air to the engines while starting them up. We were told that they werent able to repair the part so they were having some 'device' brought out to the plane to supply air to the engine so that they could get it started. I assumed this was some sort of compressor or something to that effect....knowing nothing about jet engines I assumed that they knew what they were talking about and I sat by as they proceeded to get the plane running. Something occurred to me.....if this device was required to start the engine, exactly what would they have done if the engine stalled for some reason...specifically during takeoff? If they needed some device on the ground to start to engines up again, seems to me that falling out of the sky at high speed would have been our option. As I said, I know little to nothing about jet engine operation, so I have no idea if this was a big issue, if these things stall ever, or what options a pilot has at his disposal.... so I ask you guys, the ones that know what I am talking about...was this no big deal, or am I lucky to be posting here today 
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Posted: 9/13/2005 4:15:16 PM EDT
[#1]
All current commercial airplanes can keep flying on half their engines, but I'm not 100% sure on a max-weight take-off. And you were riding a scare-bus.  Kharn |
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Posted: 9/13/2005 4:20:55 PM EDT
[#2]
We do air starts on our 737's fairly often. If the APU is out or the valve to divert air to the engines is on the fritz, it goes on the bottle. Not uncommon. Restarting at takeoff would not be fun regardless of operation of those units...it takes a while to relight the engines.
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Posted: 9/13/2005 4:22:06 PM EDT
[#3]
humm...
Sounds like Flight Attendant BS An APU [Auxillery Power Unit] more than likely is used on the ground to provide electrical power. APUs are basicaly a jet powered generator. Internaly installed in the aft section of a jet aircraft. Ventilation systems run on electrical power. And APUs are in no way used in flight for additional power. Their use in flight is Prohibited. Hot air? well, someone may have not have turned on the A/C Compressor, so it was only cycling air that wasnt cooled. That's my 2 bits... myit |
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Posted: 9/13/2005 4:23:34 PM EDT
[#4]
So if this is a fairly common thing, I guess I should assume that engines stalling out are a pretty rare event?
Please tell me this is accurate  |
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Posted: 9/13/2005 4:24:42 PM EDT
[#5]
you'd be more likely to win the lottery, than lose the engines.
Unless you fly Air Canada... LOL myit |
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Posted: 9/13/2005 4:25:51 PM EDT
[#6]
The plane was delayed over an hour....so whatever it was, something was not working correctly. We were specifically told by someone in the cabin that they couldnt start the engine....and maintenance staff could be seen coming in and out of the cabin.....not a sight one wants to see before taking off 
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Posted: 9/13/2005 4:27:39 PM EDT
[#7]
Yes
You almost died. Had the plane stalled, they would not have been able to restart the engines. This would have given the pilots one chance to land the plane, or all of you would be consumed by earth and fire. Have a nice day
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Posted: 9/13/2005 4:30:23 PM EDT
[#8]
I fly turboprops that start off of electric starter generators but I do know something about jets. Most big jet engines are started with bleed air coming from the onboard APU (small jet engine used for aux power). If a start valve sticks you might not be able to rout bleedair into the engine for start. Ever notice when they start the engines on the airliners that the AC air stops for a few minutes? All that air is being routed for engine start! They have startcarts for that reason. Happens all the time! What you said about the hot air coming out! Could have been some problem with the hear exchanger system. Im not familiar with any Airbus so this is just a guess! Hope this helps!
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Posted: 9/13/2005 4:35:24 PM EDT
[#9]
Not quite true. APU’s are used to provide AC electrical power and as a source of pressurized air for the air-conditioning packs and for starting the engines via air turbine starters. Aircraft air-conditioning systems use pneumatic air from the APU on the ground for cooling/heating and in flight from the engines. APU’s can be used in flight as an additional source of electrical power but are altitude restricted. Sounds like this plane had a PRSOV or Pressure Regulating Shut Off Valve go tits up and required a ground air start. No thing out of the ordinary, happens every day! Quib One of your many resident ARFCOM A&P mechanics. |
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Posted: 9/13/2005 4:36:15 PM EDT
[#10]
Even if the engines were to quit while in flight the pilots could start them agine in flight by using the airflow going into the engines while in flight. Its called an airstart. Besides if you were in any danger remember the captine has the final say if its safe for flight. His ass is in the plane too.
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Posted: 9/13/2005 4:36:30 PM EDT
[#11]
John Parker
An APU produces bleed air to start an engine? How about electrical power to start an engine. myit |
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Posted: 9/13/2005 4:36:39 PM EDT
[#12]
I used to work the ramp at the local airport, and we had to use start carts occasionally. It's no big deal when the APU or air diversion valve is inoperative. Just have to put the plane on ground based life support. Sometimes we had to hook up power, AC, and start cart(s).
Just made me a little nervous sometimes when we had to start the engines at the gate. It takes quite a bit of thrust to push a 250,000 lb plane through the sky, and those engines can easily kill people. |
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Posted: 9/13/2005 4:37:34 PM EDT
[#13]
Using warm air to help start a turbine engine is sometimes used during winter time. Someone else will speak to this part I'm sure.
The engines on the last two jets I've flown used internal starters to get them going, and we never needed an external unit to supply warm air to aid in engine start (even during winter ops). As for a takeoff type emergency, it would be handled in accordance with flight manual procedures. Many aircraft have procedures for takeoff emergencies that basically say, leave the aircraft alone until you are safely climbing away from the ground. I'm sure the A319 would have no trouble still maintaining a single engine climb gradient, in order to accomplish this. And restarting an engine in flight is probably easier than you think, as you have airflow causing the engine to windmill. (Of course if it was inop due to a fire, FOD/ice ingestion or catastrophic engine failure, its usually best to leave it off, unless aboslutely necessary). Engines are very smart these days. They have onboard computers which do the fuel scheduling, regulate temperatures and turbine speeds, even monitor thrust, all by themselves without the pilot even knowing. He/She just thinks that moving the throttle lever does it all. Daddy is an engineer for P&W, and I spent about a year in an AF Propulsion Shop that had handled F-15 and C-130 motors. I saw numerous F-15 motors stall during uninstalled hush house runs. So it can happen any time in the flight envelope, although it is very rare during "normal" flight parameters. During the past year, I've managed to put multi-engine jets through various stages in the flight envelope (hard Gs, through jet wash, inverted, rapid throttle movements, spins, etc), and never had an engine stall or flame out. |
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Posted: 9/13/2005 4:39:01 PM EDT
[#14]
Yes, bleed air is used to start the engine. An electric motor big enough to spin one of those giant turbines up would not be practical. Its not like hollywood in real life. James Bond does not just swing into the cockpit, flick a switch, and bring the plane to life. It takes a while for turbines to spool up. |
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Posted: 9/13/2005 4:39:08 PM EDT
[#15]
You should be happy that there was maintenance called out to fix the plane not vice versa. I’ll never understand why people are scared to see us on the plane when we’re there to fix it…….we’re there to keep you safe! Would you rather the pilot have a maintenance issue and attempt to take off anyway!
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Posted: 9/13/2005 4:39:34 PM EDT
[#16]
I remember them referring to the problem as an issue with an exchanger unit. This is sounding closer to what happened. I suppose the thing that bothers me is that I drive my truck every day...and all my vehicled before that every day for many many years. Maybe 2 or 3 times in 20 years has a vehicle not started due to a mechanical issue.....it freaks me out a bit to think that something as critical as an aircraft can have a frequest recurring issue that would make it impossible to start the engines without a 'jumpstart' from one of these devices. Call me paranoid, I would just think that something that moves 500 MPH at 30,000 ft elev might be over-enginered enough to make it more reliable than a beat up old Ford pickup 
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Posted: 9/13/2005 4:42:23 PM EDT
[#17]
QUIB & macro
Thanks for the heads up and correction. I'm flying w/ Rolls Royce engines GE, PW, etc all have their individual limitations. myit |
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Posted: 9/13/2005 4:44:52 PM EDT
[#18]
This is non-technical and based only on general knowledge of these planes, but here goes. Unless you're in the middle of takeoff at max-load, losing one engine isn't going to down that plane. It will fly and land just fine without one engine. It's possible to do a restart in mid-air, but its more likely that the captain will decide to just complete the flight on one engine (it went out for a reason--why make things worse by restarting it?) Or, if he's worried, he may divert to an alternate airport and let the ground crew sort it out later. Hopefully someone with some actual experience with this particular Airbus model will chime in.
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Posted: 9/13/2005 4:45:12 PM EDT
[#19]
You have a point I always try to remind myself that the crew that flys the plane is up there too.....so long as they arent suicidal I figure I have a pretty decent chance of coming home! |
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Posted: 9/13/2005 4:45:27 PM EDT
[#20]
Turbine engines are amazingly reliable. The event is a delay, but it's not safety related for the flight. Different aircraft have different specifics on how they start the engines. The APU provides ground power (when ground plug in isn't available or wanted). The APU is also set up to start the main engines. As mentioned above, the APU does not provide any thrust at all to the aircraft. Some aircraft do keep their APUs running during the flight, but I think that's more of a thing of the past of a few older designs. Many aircraft (particularly commercial jets) have a provision for a start cart, which is often a deisel engine on a little trailer. IIRC, once one engine is started, some jets have the ability to cross-start the other engine.
Remember, the wings do the flying, the engines provide thrust. |
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Posted: 9/13/2005 4:48:27 PM EDT
[#21]
I went to a model jet rally (and added yet another item to my hobby list if I became a gazillionaire) and watched many small jet aircraft flying around...they were anywhere from 4-8 feet in length. Very cool! Anyhoo...on some of the small aircraft, I saw electric starters, a hair dryer, and a leaf blower. Whatever gets the turbine spinning I suppose. (note for those in AZ...the AZ Jet Rally is typically in November) |
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Posted: 9/13/2005 4:49:28 PM EDT
[#22]
Wow....i expected responses, but damn...is there a limit to the knowledge base here on this site?
Thanks to all you guys that shed light on this....the issue makes a lot more sense to me know, and will probably not freak me out so much the next time it happens. Out of curiosity, as a percentage, what is the realistic chance that all the engines on a plane could fail? I would think damn near impossible...but I will defer to the experts. If all the engines went out at altitude.....could a plane land? Could the pilot glide to the nearest airport, or would the plane be pretty much screwed? |
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Posted: 9/13/2005 4:52:21 PM EDT
[#23]
I would have gotten the fuck off right then.
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Posted: 9/13/2005 5:02:22 PM EDT
[#24]
There's a chance for anything to happen. An Air Canada crew on a B767 (I believe), miscalculated how much fuel to have added. The whole liters to gallons conversion thing. They ran out of gas halfway into their flight, both engines flamed out, but they landed, just not at their destination. I also heard of a B-52 that lost 2 or 4 engines at first, then while trying to remedy the problem, they made it worse. A few were able to eject, but if I recall there was at least one casualty. You'd be surprised at how far even an airliner can glide from altitude. It will be able to land safely, and chances are, there will even be a suitable airfield within that gliding distance. However, the lower this problem happens, the worse it is! |
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Posted: 9/13/2005 5:02:34 PM EDT
[#25]
When airlines converted from piston-powered engines to turbines/jets, the minor reason was speed. Same with efficiency as that wasn't fully realized yet. What airlines were shocked to find out was the maintenance of turbines was amazing. Piston engines had to be torn down and rebuilt to a certain degree every so many hours. When airlines tore down their first turbine engine, the thing looked brand-spankin' new! Think of it this way. Your truck will drive...say...150,000 and have a good life. At 60mph, that's 2500 hours. If you average 30mph over it's life, that's 5000 hours. Aircraft fly fast, so we won't go into miles. The aircraft I was around when I was with the airlines worked an average of 10.5 hours a day (they tried for 11-12 a day). And we'll give the aircraft a month off for their maint. checks. So that's almost 3500 hours a year that the aircraft run. Give a commercial jet an average of 25 years of service and we're over 85,000 hours. The comparison to an automobile isn't even close. In addition, on my car, I have a basic idea when I last changed the spark plugs, the hoses, etc. But I don't give each and every one of them a serial number and document the history of each and every part. I have a rebuilt alternator on my car, but I don't know where it was before that. Airlines keep a history of their parts (no, not the seat cushions  . Commercial jets do need continual maintenance, and they'll last a very long time (like the B52?). If we gave an automobile the work schedule of a commercial jet, the car would being calling "uncle" very quickly. |
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Posted: 9/13/2005 5:18:07 PM EDT
[#26]
This is from one of my training CD’s, it’s a schematic of the pneumatic system on the Canadair CRJ CL65. I worked on these for 5 years at United Express. Maybe this can shed a little light on how a turbine engine aircraft pneumatic system operates.
  
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Posted: 9/13/2005 5:41:23 PM EDT
[#27]
Oooooooohhhhhhhhhh! Look at that Challanger!
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Posted: 9/13/2005 6:22:00 PM EDT
[#28]
The A319 has two AC packs and both run off of the APU bleed air on the ground when no engines are running.
The APU provides bleed air for engine start. Sounds like the APU shit itself. The interior ventilation system uses an electric motor to move either fresh air or recirculated air when the aircraft is on the ground and has no bleed air.
If you were past refusal speed and beyond abort speed and you shit an engine chances are that you would have enough airspeed and remaining engine thrust to get airborn and fly. Your rate of climb would suck ass. I don't know how the A319's rudder systems work, I would imagine that if you lose a certain percent of thrust the rudder automaticly kicks over a certain percent to keep the aircraft flying straight. At refusal / about speeds 99.9% of the time it's always better to go flying vice trying to get the aircraft to stop. |
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Posted: 9/13/2005 7:06:15 PM EDT
[#29]
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Posted: 9/13/2005 7:11:15 PM EDT
[#30]
I used to work for the first US airline that bought the Canadair RJ,they're lousey money-makers,unless the airline's charging high $$$ fares.BTW,early in the RJs life,we did alot of airstarts on RJs,its REAL funny when the guy forgets to unhook the airstart coupling from the RJ,also,a start-cart really makes a great leafblower,nice 'n loud too.
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Posted: 9/13/2005 7:15:02 PM EDT
[#31]
Canadair really thought about the ramp personell when they designed the RJ,the APU is just the perfect hight to keep rampies nice and warm on those cold CVG winter days.
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Posted: 9/13/2005 7:20:05 PM EDT
[#32]
Oh yea, not just ramp rats but mechanics too! During a snow storm the only warm dry spot on the ramp was under the APU exhaust…….and that’s right where I’d park my golf cart!
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Posted: 9/14/2005 5:47:43 PM EDT
[#33]
Yes, there have been several jet airliners that have glided to a safe landing after all engines failed. These are two airliners that ran out of gas. The Gimli Glider If a Boeing 767 runs out of fuel at 41,000 feet what do you have? Answer: A 132 ton glider with a sink rate of over 2000 feet-per-minute and marginally enough hydraulic pressure to control the ailerons, elevator, and rudder. Put veteran pilots Bob Pearson and cool-as-a-cucumber Maurice Quintal in the cockpit and you've got the unbelievable but true story of Air Canada Flight 143, known ever since as the Gimli Glider. Air Transat Flight 236 Air Transat Flight 236 was an Air Transat route between Toronto and Lisbon. On August 24, 2001 the flight ran out of fuel over the Atlantic Ocean with 306 passengers on board. |
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Posted: 9/14/2005 6:25:58 PM EDT
[#34]
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Posted: 9/14/2005 6:28:42 PM EDT
[#35]
Don't you mean inversly proportional?
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Posted: 9/14/2005 6:32:21 PM EDT
[#36]
How the hell should I know? I'm goofy on cold medicine!
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Posted: 9/14/2005 6:39:45 PM EDT
[#37]
The first one was the Gimili glider. Major FU but not nearly as bad as the AirCan that had an in-flight leak. Since this was a newer scAirbus with glass cockpit, they noticed the loss of fuel trim and did a cross transfer, dumping fuel into the leaking system! This was a trans Atlantic flight. Both engines quit when the tanks ran dry. They glided over 100 nautical miles to a dead stick landing on an AFB in the Azores!!!!! Dug some impressive ruts after the tires failed due to lack of reversers! Shut the runway for a month. Now THAT was a scary landing. But all survived. |
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Posted: 9/14/2005 6:53:38 PM EDT
[#38]
On the .mil side, I remember a Patrol Squadron 47 P-3 that lost all 4 engines near Al Masirah, Oman.
The number four prop threw a blade. The imbalance of only three blades caused the engine to explode. The prop blade was thrown from right to left and cut through the body of the aircraft, severing 35 of 44 engine and flight control cables. Four of the cables cut went to the four engines. The cutting action caused a pulling action which shut down all four engine simultaneously. The hydraulic boost handle cables were cut and the APU fuel line was cut. The nine intact cables were two aileron cables, two elevator cables, two elevator trim tab cables and two rudder trim tab cables.The co-pilot's main flight control cable was cut. www.centerseat.net/vp47crash.htm The plane ditched and the only injury was fuel burns. On a 'funny' note, the SAR swimmer refused to jump into the water to help the floaters into the helicopter harness. When asked later he said he didn't feel comfortable jumping into the middle of the schools of sharks that were circling the liferafts.  Fritz P-3/C-130 ResTycom in exile at NSA Millington |
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Posted: 9/15/2005 5:16:52 AM EDT
[#39]
I saw documentaries about both the Gimli Glider and the Air Transat Airbus. The Air Transat one is coming up again on 09-20. National Geographic Channel Flying on Empty An Air Transat Airbus runs out of fuel over the Atlantic and has to glide to a power-free landing. Air Emergency explores the causes that contributed to this near catastrophe and shows how the crew managed to glide to a safe landing. Also airs: Wednesday, September 14, 2:00A Tuesday, September 20, 2:00P |
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Posted: 9/15/2005 5:25:26 AM EDT
[#40]
Care to be a little more specific to type. I know quite a few planes where that statement is dead wrong. |
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Posted: 9/15/2005 5:43:48 AM EDT
[#41]
I pointed that out as well ,on page one. The APU’s I’m familiar with as an A&P are altitude restricted but not prohibited. Where are all the ARFCOM CPL holders to back up this thread! |
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Posted: 9/15/2005 5:51:39 AM EDT
[#42]
I believe there are some similarities but it’s still a CRJ 200! I’ve since moved up to it’s older brother, the CRJ 700.  But there’s still big brother out there……..the CRJ 900! 
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Posted: 9/15/2005 5:59:14 AM EDT
[#43]
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Posted: 9/15/2005 7:11:31 AM EDT
[#44]
Pray tell where the APU in a Boeing 727 is? |
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Posted: 9/15/2005 7:27:46 AM EDT
[#45]
I quit flying in late 2000 I guess I do not count anymore. Every heavy type I was rated on, APU's could be used in flight. |
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Posted: 9/15/2005 7:33:01 AM EDT
[#46]
Was an APU not available when the 727 was first introduced? "The auxiliary power unit, or APU in the Boeing 727 is a small turbine engine mounted between the main wheel wells. it draws air from the wheel well area for combustion and cooling and exhausts through louvers in the top of the right wing root." www.boeing-727.com/Data/systems/infoapu.html |
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Posted: 9/15/2005 7:38:47 AM EDT
[#47]
Can't, you cause 'trouble' in ANY way and your a terrorist.
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Posted: 9/15/2005 7:49:42 AM EDT
[#48]
The depth of knowledge here will never cease to amaze me.
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Posted: 9/15/2005 2:03:43 PM EDT
[#49]
True, true. An APU was a complete afterthought on the 727. Infact it is the only aircraft I know of that the APU is not to be used in flight. (due to it's location) Also an interesting tidbit is that if you were to do an APU fire test while it is running, you will initate an auto shutdown. Just don't always make sweeping general statments. The 727 will show to be the exception to several rules when it comes to aviation. |
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Posted: 9/15/2005 2:19:43 PM EDT
[#50]
I saw that too...IIRC it was an episode of "Seconds From Disaster" |
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