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Using The Air Truck To Start My 737 Flight Today  
User currently offlineEwmahle From United States of America, joined Mar 2005, 109 posts, RR: 0
Posted (6 years 2 months 3 weeks 1 day 8 hours ago) and read 9537 times:

Good eveing all. I just returned from PHL on US Flt. 1460 to RDU. In PHL our 737 was started at the gates using the air truck. I had seen this done once before on a UA737 but I have never been on a flight in which this has happened nor do I really understand why it is done.

Can anyone provide a resonable explanation as to why the pilot, or the ground crew, would decide to start the engines this way and what exactly happens when they do it? I am not looking for a technical answer, just general resoning.

Thanks

64 replies: All unread, showing first 25:
 
User currently offlineZANL188 From United States of America, joined Oct 2006, 3433 posts, RR: 0
Reply 1, posted (6 years 2 months 3 weeks 1 day 7 hours ago) and read 9522 times:
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The APU is probably inop. The engines need hi pressure air to run the starters, which the apu would normally provide.


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User currently offlinePhxpilot From United States of America, joined Jul 2005, 78 posts, RR: 2
Reply 2, posted (6 years 2 months 3 weeks 1 day 7 hours ago) and read 9519 times:

Air carrier size jet engines are started using compressed air. This air can come from the APU or a ground source. The compressed air turns a miniature turbine which is connected to the high pressure compressor. To start the engine the high pressure compressor is driven to a given percentage of rotation by the starter through the use of this compressed air. Fuel is then introduced along with a spark. Once lightoff occurs, the engine is accelerated through a combination of the starter plus the expanding exhaust gasses. Upon reaching a given percentage of rotation, the starter cuts out and the engine becomes self-sustaining.

The reason you would need an external source of compressed air on a 737 is if the APU was inoperative.

(ZANL188 beat me to it by 1 minute)

[Edited 2008-01-28 16:34:56]

User currently offlinePHLapproach From Philippines, joined Mar 2004, 1231 posts, RR: 20
Reply 3, posted (6 years 2 months 3 weeks 1 day 7 hours ago) and read 9491 times:

UGHHH, my ears are bleeding just thinking about my companies air start trucks. One little I would like to add, A&P's use to do air starts. But now it's fleet service that does them.

User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 4, posted (6 years 2 months 3 weeks 1 day 7 hours ago) and read 9488 times:

Those things can get LOUD! Huffers as we ramp rats call them is used quite often. Sad, but at ASA, I used one atleast once a day to start of an RJ with an INOP APU.


What gets measured gets done.
User currently offlineEwmahle From United States of America, joined Mar 2005, 109 posts, RR: 0
Reply 5, posted (6 years 2 months 3 weeks 1 day 7 hours ago) and read 9429 times:

Thanks for your quick responses. So an In-Op APU is presumably not of any immediate concern to the well-being of the Airliner, so then when will they take the time to fix or replace the APU? Is it something they could do at the end of the day and have running again by the next morning or will US simply wait until the plane can be taken out of service and put in to MX?

User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9378 posts, RR: 52
Reply 6, posted (6 years 2 months 3 weeks 1 day 6 hours ago) and read 9401 times:



Quoting Ewmahle (Reply 5):
So an In-Op APU is presumably not of any immediate concern to the well-being of the Airliner, so then when will they take the time to fix or replace the APU? Is it something they could do at the end of the day and have running again by the next morning or will US simply wait until the plane can be taken out of service and put in to MX?

It really depends on the airline. A 737 can fly without an APU, but it is something that should be fixed in a relatively short manner. RJs often will go longer periods of time without an APU, but on the 737, the APU is an important thing to have. It is an ETOPS requirement since it is the only source of power should there be a duel engine failure. Also not all stations have the ability to perform a ground cart air start on a 737, so the APU would likely be replaced in short order.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineFlyMatt2Bermud From United States of America, joined Jan 2006, 563 posts, RR: 7
Reply 7, posted (6 years 2 months 3 weeks 1 day 6 hours ago) and read 9387 times:

I heard a DC8 crew in the Middle East actually convinced a fire rescue vehicle to spray high pressure water through an outboard engine to get it turning enough to start the engine. The ground huffer and aircraft APU were both inop. It was not an approved procedure and the word was the captain was disciplined, but he made his schedule so his punishment wasn't too severe. I have put in a call to the guy who gave me the story, perhaps he can elaborate.


"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
User currently offlineFr8mech From United States of America, joined Sep 2005, 5098 posts, RR: 12
Reply 8, posted (6 years 2 months 3 weeks 1 day 4 hours ago) and read 9349 times:



Quoting ZANL188 (Reply 1):
hi pressure air to run the starters

I hate to nitpick, but I will...the aircraft starter uses a high volume of relatively low pressure air (35-45 psi).

Quoting Ewmahle (Reply 5):
Is it something they could do at the end of the day and have running again by the next morning or will US simply wait until the plane can be taken out of service and put in to MX?

An APU is normally a catergory C MEL item. That means it can go 10 days until it must be fixed, with an extremely few exceptions.



When seconds count...the police are minutes away. Never leave your cave without your club.
User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 9, posted (6 years 2 months 3 weeks 22 hours ago) and read 9234 times:



Quoting Ewmahle (Thread starter):
Can anyone provide a resonable explanation as to why the pilot, or the ground crew, would decide to start the engines this way and what exactly happens when they do it

B737 Powerplant uses an Air starter,which needs compressed air to start from either the APU,other Engine or Ground pneumatic cart.
In this case the APU was u/s or APU pneumatics was u/s hence the use of the ground cart.

regds
MEL



Think of the brighter side!
User currently offlineTristarSteve From Sweden, joined Nov 2005, 3930 posts, RR: 34
Reply 10, posted (6 years 2 months 3 weeks 22 hours ago) and read 9228 times:



Quoting RoseFlyer (Reply 6):
It is an ETOPS requirement since it is the only source of power should there be a duel engine failure.

ETOPS does not cater for dual engine failure!
On some aircraft the APU is required for ETOPS, like B737, but on aircraft that are designed for ETOPS the APU is not required.
On B777 the APU can be inop for an ETOPS departure. Each main engine has a Back up generator which is there to cater for engine failure in the cruise.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 11, posted (6 years 2 months 3 weeks 19 hours ago) and read 9180 times:

Some cool air starter stuff in this article (my favorite a.nut article): http://www.airliners.net/articles/read.main?id=52


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9378 posts, RR: 52
Reply 12, posted (6 years 2 months 3 weeks 16 hours ago) and read 9121 times:



Quoting TristarSteve (Reply 10):
ETOPS does not cater for dual engine failure!

Yes that is correct. I think I worded my statement incorrectly. On airplanes without a RAT, the APU is usually required for ETOPS. Should there be an engine failure and an IDG failure on the other engine, the plane would be dead if it didn't have an operable APU. I wasn't referring to the case of both engines failing, but rather electrical or hydraulic failures.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 13, posted (6 years 2 months 3 weeks 16 hours ago) and read 9118 times:



Quoting RoseFlyer (Reply 12):
On airplanes without a RAT, the APU is usually required for ETOPS.

The B757 has a RAT & ETOPS would need a serviceable APU.
regds
MEL



Think of the brighter side!
User currently offlinePilotpip From United States of America, joined Sep 2003, 3139 posts, RR: 11
Reply 14, posted (6 years 2 months 3 weeks 16 hours ago) and read 9109 times:



Quoting FlyMatt2Bermud (Reply 7):
I heard a DC8 crew in the Middle East actually convinced a fire rescue vehicle to spray high pressure water through an outboard engine to get it turning enough to start the engine. The ground huffer and aircraft APU were both inop.

I know that a few existed, but most DC-8s don't have APU's. The ones that did had all kinds of issues.

EMB-145s have very unreliable APUs. For passengers the most discomfort will be caused by the inability to have the packs heating/cooling the cabin during a turn.



DMI
User currently offlineA10WARTHOG From United States of America, joined Jul 2004, 324 posts, RR: 0
Reply 15, posted (6 years 2 months 3 weeks 16 hours ago) and read 9106 times:



Quoting Pilotpip (Reply 14):
EMB-145s have very unreliable APUs. For passengers the most discomfort will be caused by the inability to have the packs heating/cooling the cabin during a turn.

What model APU do you have the C-11 or C-14? The C-14 is alot better then the earlier C-11. They still fail, but not as much and in two years of working on them they have gotten a lot better. Once Sundstrand figure out they had a FADEC problem, the solder joints on the boards where breaking. This was only found in service and not a test bench until they started opening them up.


User currently offline777WT From United States of America, joined Jan 2005, 874 posts, RR: 1
Reply 16, posted (6 years 2 months 2 weeks 6 days 16 hours ago) and read 8871 times:



Quoting Pilotpip (Reply 14):
EMB-145s have very unreliable APUs. For passengers the most discomfort will be caused by the inability to have the packs heating/cooling the cabin during a turn.

I would say the CRJ-200 APU are the worst of all! and that includes the APU intake door!


User currently offlineDALMD88 From United States of America, joined Jul 2000, 2503 posts, RR: 14
Reply 17, posted (6 years 2 months 2 weeks 6 days 12 hours ago) and read 8797 times:



Quoting Ewmahle (Reply 5):
Thanks for your quick responses. So an In-Op APU is presumably not of any immediate concern to the well-being of the Airliner, so then when will they take the time to fix or replace the APU? Is it something they could do at the end of the day and have running again by the next morning or will US simply wait until the plane can be taken out of service and put in to MX?

Most operators will try to get an inop apu fixed as quick as possible. They would most likely reroute the aircraft so it can overnight at a capable mtc station within a day or two. This gives you a few times to troubleshoot and line up any parts before the MEL runs out. Operationally an inop apu air source is a bit of a pain for ramp. It is a possible cause for delays. You now have to round up a start cart and hope that it works.


User currently offline777WT From United States of America, joined Jan 2005, 874 posts, RR: 1
Reply 18, posted (6 years 2 months 2 weeks 6 days 11 hours ago) and read 8763 times:



Quoting DALMD88 (Reply 18):
Most operators will try to get an inop apu fixed as quick as possible. They would most likely reroute the aircraft so it can overnight at a capable mtc station within a day or two. This gives you a few times to troubleshoot and line up any parts before the MEL runs out. Operationally an inop apu air source is a bit of a pain for ramp. It is a possible cause for delays. You now have to round up a start cart and hope that it works.

One time there was a a/c that had problems accepting GPU...they deferred the GPU and had to use the APU for the time...until they went to BUF...then the APU spitted out a fireball then parts was shooting out of the tail while at the gate.

They sent a road trip...attempted to fix the GPU system, attempted to start the plane by powerng it up on batteries then airstart it...this set off a engine exceedence message which was a no go...resetting it while the engines was running didn't work.

So back to fixing the GPU, they didn't figure it out until a few days later someone crossed the wires installing the GPU socket in the plane.


User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 19, posted (6 years 2 months 2 weeks 6 days 11 hours ago) and read 8761 times:



Quoting DALMD88 (Reply 18):
You now have to round up a start cart and hope that it works.

Why hope.Even GSEs have a Fixed Mx schedule.
regds
MEL



Think of the brighter side!
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 20, posted (6 years 2 months 2 weeks 6 days 11 hours ago) and read 8758 times:
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Quoting HAWK21M (Reply 20):
Why hope.

Involved in another bet already, Mel?  eyebrow 

2H4



Intentionally Left Blank
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 21, posted (6 years 2 months 2 weeks 6 days 9 hours ago) and read 8728 times:



Quoting HAWK21M (Reply 20):
Why hope

Because the time you find out that a huffer or a GPU is inop is usually the same time you need it most.

Quoting 777WT (Reply 16):
I would say the CRJ-200 APU are the worst of all!

My experience with them was quite good. Just don't start them above FL250.

Quoting Pilotpip (Reply 17):
I noticed quite a few recently that were just SCREAMING,

This is part of how the ERJ earned the WSCOD nickname.



Proud OOTSK member
User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 22, posted (6 years 2 months 2 weeks 5 days 21 hours ago) and read 8635 times:



Quoting 2H4 (Reply 21):
Involved in another bet already, Mel?

Bad habit .... heres compensation ???
 wink 

Quoting Lowrider (Reply 22):
Because the time you find out that a huffer or a GPU is inop is usually the same time you need it most

Not really.If mantained as per approved scheduled & tested daily,the chances are less.

regds
MEL



Think of the brighter side!
User currently offlineGreasespot From Canada, joined Apr 2004, 3076 posts, RR: 21
Reply 23, posted (6 years 2 months 2 weeks 5 days 9 hours ago) and read 8564 times:

We called it giving the plane a blowjob in the hangar......Imagine the explaining i had to do when I radioed out that I would be there in 10 mins go give the plane a blowjob.....oops....but it was funny as hell after all appologies to ground freq for my slip up...

GS



Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
User currently offlineReidYYZ From Kyrgyzstan, joined Sep 2005, 536 posts, RR: 0
Reply 24, posted (6 years 2 months 2 weeks 5 days 6 hours ago) and read 8530 times:

At one of my former employers, they had a length of hose with a coupling at each end. One coupling had a fork protruding that would hold open the split flapper check valve open. The aircraft with the U/S apu got the regular coupling hooked up. The a/c with the servicable apu was hooked up with the forked coupling, with the apu off or maybe bleed off (not sure, been too many years). Starting the apu, with the flappers held open, you could get a cross bleed start from the one aircraft to the other, no jet starter required. I saw it work once with a pair of B727's.

25 BritPilot777 : Am I right in thinking that (basic step by step), the air start would blow air into the engine, thus turning N1 and the following rotors / stators com
26 MD11Engineer : No. You blow the air into a starter, which is a miniature turbine running at very high speed (around 100.000 rpm). This roation is reduced in the sta
27 Airgypsy : The 727 was designed without an APU. (Initially it was design with only two engines. This is why the APU is in the RH wheel well. No CG margin left fo
28 TristarSteve : I wish you guys would stop saying this. Maybe no APU no ETOPS on your aircraft. Our B767 requires APU for 180min ETOPS, but with 138min ETOPS APU can
29 Starlionblue : Apparently those could sometimes blow a huge tongue of flame around the wing. Must have made for several brown trouser moments among the pax.
30 HAWK21M : I always found High volume "Ideal" Three hoses for starting a B757 with RB211-535 Engines very disapointing. although We do it with Two,thanks to the
31 Wirelock : hey all, the apu engine start cxan be inop for a number of reasons.. not just APU INOP. it could be something as simple as the apu bleed pushbutton sw
32 Post contains images ATCT : Yea, We did the airstarts at DL (ramp rats). Clint Nothing like the sound of a 30 yr old airstart starting up the 5:30AM Md-80 to ATL That'll wake eve
33 ReidYYZ : Just to add to it, the starter turns the N3 rotor on RR. This is of course not for you, MD11, it's for those who don't know. In engine run procedures
34 Rfdramp : I have no idea how anyone near RFD can sleep during December. UPS usually has at least 5 airstarts running from 1AM-3AM. Combine that with all the AP
35 Pilotpip : One's hourly wage correlates directly. When that hourly wage is so low that turnover is rampant, and people are not adequately trained they don't do
36 Cancidas : which trucks do you guys have? we've had the old stewart & stevenson huffer carts forever in LGA, they work better than the new ones that keep breaki
37 EssentialPowr : A stereotype? Apparently your 1st post about a "$6/hr ramper" has been deleted, so I believe my point has been made.
38 N231YE : Could it also be that the APU was not running in the first place, to save fuel? I know at CLE, YV (operating as UA Express) almost always started thei
39 Post contains images HAWK21M : Interesting term "Buddy starts" I think I'll use it often. Out here we call it Aircraft to Aircraft pneumatic starts. Very usefull if there is no Air
40 JayDub : We just called it "giving the plane a blow job".
41 Post contains images WILCO737 : Very nice WILCO737 (MD11F)
42 474218 : In the USAF the air start cart part number was as the "MA1A". Just outside Kadena AFB, Okinawa was a street called MA1A Alley. Its where you when to
43 777WT : Isn't there a check valve in the air start system that prevents the air from coming out the air start connection? I thought there was another one hig
44 HAWK21M : Thats true on both B737 & B757s. The Check valve is on top. regds MEL
45 Post contains images Seabosdca : Hmm.... fixing broken cart... fart start cart art?
46 Lowrider : What would the implications of a hung start be in this scenario?
47 777WT : That said, so there would be no loss of air during a crossbleed start via the air start connection nozzle. I don't see how this can work ie if you wa
48 HAWK21M : There is an Adapter available that manually pushes the Checkvalve open in such cases for aircraft to Aircraft starts. regds MEL
49 MD11Engineer : We regularly do pack heat exchanger washes during our A-checks on the 737NG (cleaning the heat exchangers in the ram air ducts). This is done by open
50 HAWK21M : Interesting.We still use an External Pneumatic source for the HE Cleaning. regds MEL
51 BR715-A1-30 : I remember when the 717 first came out, ATL was doing up to 5 a day on the 717s due to INOP APUs. In the short time I worked at FL we had to do two wi
52 Copter808 : Sometimes referred to as "A blowjob to go!"
53 A10WARTHOG : [ The ERJ have one, put there is a tool much like a big clothes pin that holds them open when you go a plane to plane start. Never did one or seen one
54 ReidYYZ : Uhm, I thought I covered this 3 weeks 18 hours 25 minutes ago: There can't be a check valve deeper in the system (leading to the starter) otherwise c
55 DC-10Tech : The APU simply provides air for AC or engine starting and electrical power on the ground. It can also provide these in flight if it is certified to d
56 N353SK : When I worked for Skyway the Huffer procedure was awful! It went something like this: Bury the foam earplugs as deep as they can go Borrow a pair of E
57 Arv79 : On a related note, would the APU be able to deliver enough air to start two or more engines at the same time?
58 TristarSteve : Yes. Used regularly on B744 and B777.
59 DC-10Tech : I would guess the behemoth 747 APU could do this, but most of them don't put out enough air to pull this off. You might be able to crank two at a tim
60 Arv79 : Thank you both. I haven't seen the APU air inlet on the 747 but to me the 777 inlet didn't seem big enough to pull enough air to start both engines at
61 Tdscanuck : The air drives the mechanical device to start the engines. The starter is an air turbine with a bunch of reduction gearing that spins the HP spool vi
62 L-188 : Haven't seen that, I have seen a Lockheed Electra started by using the jet wash from a 727 to get the prop spinning fast enough.
63 DC-10Tech : The start switch opens the start valve, which lets the air (from the APU, start cart, or from another engine) spin the starter (which is basically a
64 HAWK21M : Are you talking about Triple spooled Powerplants too. regds MEL
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