Phxplanes From United States, joined Feb 2005, 412 posts, RR: 0 Posted (2 years 3 months 1 week 3 days 17 hours ago) and read 2484 times:
Like the title says I have some questions about air starts. First how does the pilot know they will need an airstart. Why do you need an airstart, what happens to need it. Finally what exactly does the air start machine do (obviously blows air into the engine) but more technical.
Sorry the question might be a little choppy but thank you in advance for the answers.
N685FE From United States, joined Dec 2003, 309 posts, RR: 12 Reply 1, posted (2 years 3 months 1 week 3 days 16 hours ago) and read 2478 times:
Aircraft engines are started using an air driven starter that receives pneumatic pressure from the apu. If the bleed system on the apu or the entire apu is on deferral then an alternate source of air pressure is needed. When a new crew receives the aircraft they review the log book, any deferrals will be noted in the log book with a deferral sticker next to the apu start switch. Need more details?
KAUSpilot From United States, joined Jan 2002, 1668 posts, RR: 34 Reply 2, posted (2 years 3 months 1 week 3 days 16 hours ago) and read 2472 times:
Quoting Phxplanes (Thread starter): Like the title says I have some questions about air starts. First how does the pilot know they will need an airstart. Why do you need an airstart, what happens to need it. Finally what exactly does the air start machine do (obviously blows air into the engine) but more technical.
Sorry the question might be a little choppy but thank you in advance for the answers.
You know you will need an airstart if your APU is inoperative. Normally the APU provides the air needed to start the engines, however, if it isn't working, then you will need an airstart cart. Some military aircraft always need an aircart start, as the they don't want to or can't use the batteries to start the engines and aren't equipped with APU's (the T38 comes to mind).
The airstart cart really doesn't do a whole lot more than blow air into the engine. The Airstart hookup is plumbed into the air turbine starter via a "starting control valve". This valve regulates the pressure supplied to the air turbine starter (ATS). The ATS in turn converts the pneumatic energy from the pressurized air into driving torque for engine gas generator spool acceleration up to the self-sustained speed during the starting cycle. Air exhaust from the turbine is discharged into the engine nacelle compartment. There is not a significant difference in the start sequence between using the APU as a pneumatic source vs. an airstart cart, at least on the aircraft I fly.
We must start the #2 engine on my aircraft first if we are using an airstart cart, since the hookup is on the right side of the aircraft and it is plumbed into the #2 engine's ATS. After starting the #2 engine, the airstart cart is disconnected.
To start #1 after an aircart start, we do what's called a "crossbleed start", meaning we run the #2 engine up to 83% N2, open the bleed air valve and crossbleed, and start #1 using bleed air provided by #2. Special caution must be exercised during this procedure so as not to damage nearby aircraft or ground equipment with jetblast.
N8076U From United States, joined Jun 2006, 425 posts, RR: 8 Reply 3, posted (2 years 3 months 1 week 3 days 16 hours ago) and read 2460 times:
One other thing, is some older aircraft didn't even have APU's, like the DC-8 (some had them added later, but the majority didn't), so every start would require the air cart/truck to be hooked up, and one engine started at the gate before pushback. Once pushed back, the bleed air from the one running engine would be used to start the remaining ones.
EMBQA From United States, joined Oct 2003, 7330 posts, RR: 11 Reply 4, posted (2 years 3 months 1 week 3 days 12 hours ago) and read 2432 times:
Quoting Phxplanes (Thread starter): Like the title says I have some questions about air starts. First how does the pilot know they will need an airstart. Why do you need an airstart, what happens to need it. Finally what exactly does the air start machine do (obviously blows air into the engine) but more technical.
To answer your questions-
The APU won't start....APU failure....you go find the Air Start Cart....it's an APU and produces the air needed to start the aircraft engines when the APU won't work.....nothing technical about it, the plane just gets its air from a second source.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
N685FE From United States, joined Dec 2003, 309 posts, RR: 12 Reply 6, posted (2 years 3 months 1 week 3 days 5 hours ago) and read 2361 times:
GE-CF680C2A5F
General-The starting system of the CF6-80C2A FADEC engine utilizes pressurized air to drive a turbine at high speed. The turbine turning through a reduction gear applies a torque to the HP shaft, thus driving the engine. The air which is necessary to drive the starter is supplied by either : - the APU - crossbleed from the second engine - a ground power unit. The starter supply is controlled by a starter shuf-off valve pneumatically operated and electrically controlled. In case of failure, the valve can be opened manually. Engine starting is controlled from ENGINE START panel, located in the center of the overhead panel. For each engine, the illumination of the blue OPEN legend integral with ENGINE START/START 1 (2) pushbutton switch indicates that the start valve is open. The starting sequence may be interrupted at any time by placing ENGINE START selector switch in OFF position. This ignition selector switch also controls the ignition system and enables selection of one of the two ignition systems (A or B), or both at the same time or a dry motoring to be carried out with CRANK selected. A switch in the N2 speed indicator causes the starter valve to close when the N2 speed exceeds 45 %. The starter centrifugal cluth then disconnects the starter turbine and gears from the output shaft and allows the turbine to stop rotating.
Air Supply-The air necessary for starting comes from the duct connecting engine bleed and the pre-cooler via a 4 in. dia. duct. This duct is attached to the engine bleed duct just before the precooler inlet. Through operation of the crossfeed valve and APU bleed valve, the air necessary for the starter is supplied by either : - crossbleed from the other engine - the APU and in that case, all the air bled from the APU is used for starting - an external source able to supply a pressure between 25 and 55 psig (maximum permissible pressure in the duct).
FlyMatt2Bermud From United States, joined Jan 2006, 520 posts, RR: 5 Reply 10, posted (2 years 3 months 1 week 2 days 16 hours ago) and read 2229 times:
We typically only require a aux ground air start when the airstart cart is not available. It's Newton's law.
"I just want you to know, we're all counting on you!"
HAWK21M From India, joined Jan 2001, 25408 posts, RR: 52 Reply 11, posted (2 years 3 months 1 week 2 days 14 hours ago) and read 2222 times:
Its normally reffered to as the Pneumatic Jet Starter unit.
In case an Aircraft has an Unserviceable APU,or APU that has an u/s Pneumatics.The Pneumatic Jet Starter is used.
Depending on the Requirement of Airflow as per Engine to be started.The Unit can be of a certain Capacity,with Two hoses.These hoses attach to Ground connectors of the Aircraft.
The Pneumatic Jet Starter is almost a Truck mounted APU.The Pneumatic Supply is used to Crank the Pneumatic starter mounted on the Engine & crank it to achieve necessary Start.
Undehoulli From , joined today!, posts, RR: Reply 12, posted (2 years 3 months 1 week 2 days 8 hours ago) and read 2187 times:
Quoting GEG (Reply 5): Roughly how much air pressure is required for the start?
The aircraft I fly requires 12 PSI for starting the engines, either from the APU or from an air cart. I've never had to use an air cart, and I usually see around 35 PSI from the APU.
Charlienorth From United States, joined Jun 2006, 923 posts, RR: 3 Reply 14, posted (2 years 3 months 1 week 2 days 5 hours ago) and read 2165 times:
A-320 with CFM56 >25 psi, someone asked about APU's breaking,some seem to die if you look at them wrong!They're real susceptible to shutting down at low oil levels,there was an airline I worked on-call for,CRJ's,Maint control would call about a failed APU and often we would service the oil level and the thing would then operate normally,the sad thing was it usually just out of a line-check,pressure switches are another high failure item,apu door rigging seemed to be a problem on the 737/200,speaking of APU's anyone up for a APU flow control valve on a 727?
"The right decision at the wrong time is still the wrong decision" Hal Carr
Nonfirm From , joined today!, posts, RR: Reply 16, posted (2 years 3 months 1 week 1 day 14 hours ago) and read 2091 times:
We use the air start cart or (huffer) as we call it for any Eng start the the whole apu is on Mel or the pneumatics system is inop.If the electrics on the apu is inop then we use apu air but ground power to complete the start then a cross-bleed to start the opposite Eng.We also only start the # 1 Eng at the gate because the huffer is on the r/h side of the a/c due to the pluming and safety for the ground crew.
UAL Bagsmasher From United States, joined Sep 1999, 2041 posts, RR: 10 Reply 17, posted (2 years 3 months 1 week ago) and read 2015 times:
The CRJ-200 APU is probably worth more in scrap metal than as an APU. Well, maybe not that bad, but close. I guess it's good job security though. I second the motion about bad pressure switches. They go bad all the time, and leak oil more often than not.
Life of CRJ-200 A&P= PRESENT: NO SDN...ERR CODE: 109...LRU: DOOR...INHIBIT*
FlyMatt2Bermud From United States, joined Jan 2006, 520 posts, RR: 5 Reply 21, posted (2 years 3 months 5 days 9 hours ago) and read 1936 times:
Quoting TWAL1011727 (Reply 18): Quoting FlyMatt2Bermud (Reply 10):
We typically only require a aux ground air start when the airstart cart is not available.
Could you tell us what the difference between the two are?
Sponsor Message: 
From United States, joined Feb 2005, 412 posts, 
From India, joined Jan 2001, 25408 posts, 
From , joined today!, posts, 