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cskafan123
6th Feb 2010, 11:33
Guys,
I am getting confused on some issues for ATS limitations.
How do you understand he following limitation?


Starter engagement limitations:
Start # engagement time cooling period
1 30 sec none

Does that mean that if there is no N2 rotation by the time of 30 sec I need to abort?or does that mean that by 30 sec it has to reach starter cut out speed ?
Is this the main reason why we start clock when starting engines?

Thanks a lot.

hetfield
6th Feb 2010, 11:50
Don't know which type/engine you are asking but I understand it that way starter may run up to 30 sec without onward cooling.

No N2, no starter activity.

cskafan123
6th Feb 2010, 12:01
The engine is GE CF34-3B engine for CL 604.
So then how do you know when to abort start?There must be a plain answer about engine starting/time sequence.:ugh:

hetfield
6th Feb 2010, 12:08
Don't know that engine. On JT8, CF 6 e.g. it's about that way

- starter engagement, start timing
- N2 rise, for whatever reason the starter may run for 30 sec without cooling
- if longer than 30 sec observe cooling time/number of attempts
- if no N2, no starter engagemnent, no cooling time

capt. solipsist
7th Feb 2010, 03:23
I believe your limitations mean that for the 1st start attempt, you can leave the starter engaged for 30 secs. max. before aborting start (for whatever valid abort start reason). After which, you can make another start attempt right away. For subsequent attempts, it doesn't specify anymore.

V1... Ooops
7th Feb 2010, 06:55
I believe that starter engagement time limitations for most engines are not published primarily to limit the time the pilot uses the starter for a normal engine start, they are published to limit the time that a maintenance technician uses the starter for dry motoring, engine washes, and other non-flight related activity.

Common sense suggests that when the aircraft manufacturer publishes a starter engagement time limit, they will have ensured that the limitation allows sufficient time for a normal engine start. Thus, if pilots are running up against the starter time limits, this suggests that the there is a problem elsewhere that needs to be investigated - in other words, why is it taking longer than normal to start the engine?

Just food for thought.

Tinwacker
8th Feb 2010, 13:24
CSK
Does that mean that if there is no N2 rotation by the time of 30 sec I need to abort?

Without knowing your engine type I would have aborted the start long before 30secs. If no N2 either indication fault, starter valve not opened or starter drive has sheared.
Engines that I am familiar with would have after start selection, 1-2 secs starter valve OPEN indication then N2 indication.

Further, the time during starter selection is recorded primarily for starter motor duration limitation for the required amount of cooling before next start.
Another time that is noted will be the 'fuel ON time' and if more than say 20-30secs abort the start as engine has not lit.
Maybe ignitor fault, on side selection or fuel fault. After engine has run down the second start would utilise ign BOTH for the second attemp.

maintenance technician uses the starter for dry motoring

and the pilot when a wet start has occurred, to clean the engine of unburnt fuel before second attemp, also to cool the engine down prior to fuel ON if say engine EGT greater than 100'C or what ever your engine requires after a short hot transit.

A typical Air Turbine Starter duration would be
3mins ops then 1min cooling
3mins ops then 1min cooling
3mins ops then 30mins cooling for example
or
5mins ops then 30mins cooling possibly used during tail pipe fire or other emergency.

Clearly a good normal start would be completed well before the 3mins applied.



TW

411A
8th Feb 2010, 13:44
I believe that starter engagement time limitations for most engines are not published primarily to limit the time the pilot uses the starter for a normal engine start, they are published to limit the time that a maintenance technician uses the starter for dry motoring, engine washes, and other non-flight related activity.


A completely reasonable presumption which makes perfect sense, except...on one type of engine (early RB.211 Rollers) there were no maintenance starter limitations originally published, and indeed maintenance folks would often dry run the engine for extended periods, without any noted problems.
Pilots, on the other hand, did have starter limitations for normal line ops, and these were observed...to the complete bewilderment of maintenance folks.:}

Clearly a good normal start would be completed well before the 3mins applied.


Ahhh well, not always, especially on very cold mornings with one specific type...early varients of the three-shaft RB.211.
Often times in these corcumstances, engine starts completed by lunchtime would be a major accomplishment, to the complete bemusement of many ground folks who thought we had somehow slipped back into the piston airliner mode, as we made much smoke, during engine start...and still do.
Type, TriStar.

Tinwacker
8th Feb 2010, 14:01
411A

a good normal start
but normal doesn't mmmm include the early 211-22Bs - should do as the starter is being continually caned, not so good.

Then starter oil changes and servicing were increased accordingly on the 211.
Luckily the later 211s are a bit quicker off the mark but yes not rapid.

TW

Beeline
8th Feb 2010, 14:33
Most modern engines require an inspection of the starter if the duty cycle has been exceeded for a length of time. Most have magnetic chip detectors on the drain plug, too check for debris.

Other checks include crash engagement at certain N2/N3; even though sometimes there isnt much left too inspect if the clutch pawls havent rengaged with the starter gearing.

N2/N3/start time defo worth a check, may not be the starter u/s but the driveshaft connecting the gearbox to the engine shaft. Recent problem with a certain engine manufacturer. Oil px seen but rapid rise in N-speed indicating runaway.

gas path
8th Feb 2010, 15:43
N2/N3/start time defo worth a check, may not be the starter u/s but the driveshaft connecting the gearbox to the engine shaft. Recent problem with a certain engine manufacturer. Oil px seen but rapid rise in N-speed indicating
That'll be SQ's Trent's at LHR the other week then!:p