View Full Version : Starter Cranking Limits
Curious to know how exactly the limits are determined during certification?
I know it could be hard to find the right answer to this but many 'Thanks' in advance for those who reply :) .
barit1
7th Mar 2005, 02:06
I do not have data for any specific commercial aircraft, but can cite an experience with a carrier-based Navy bird.
There was at least a 5-minute continuous crank permissible, as long as starter air temperature limits were observed. This was useful for a compressor wash procedure (not a bad idea in salt air environment).
However, if the hydraulic system were loaded (e.g. for wing fold/unfold), the duty cycle was much shorter. This made it impractical to use the starter to run hydraulics.
So it all depends on the installation characteristics.
Well, for the Lockheed TriStar, it is...
Three minutes ON, one minute OFF.
Repeated again, then thirty minutes OFF
This was for the pilots/flight engineers info.
A look in the maintenance manual provided something quite different, for ground engineers...15 minutes on, thirty minutes OFF.
Always wondered why.:}
barit1
7th Mar 2005, 18:23
It could well be APU vs facility or cart air - different temperatures.
sgt_pepper
7th Mar 2005, 20:36
For the MD-11 with GE 80C2D1F and PW 4460/62:
1st attempt - 5' on and 30" off for each minute on.
2nd attempt - 5' on and 10' off.
3rd attempt - 5' and then give up.
Starter reengagement:
GE - Normal: N2 below 20%. Emergency: as high as 30%.
PW - Normal: N2 below 15%. Emergency: as high as 20%.
s_p
GotTheTshirt
7th Mar 2005, 20:59
The stater limitations are because of overheating the starter which apart from transfering a considerable amount of energy is also receiving hi temp air in some cases like bleed starts.
L1011 starter cycle limitation as follows:
BA and GF Pilot operating notes show 2 cycles of 3 minutes on with 1 min off plus 1 cycles of 1 min then 30 minutes cool
Alternatively 5 minutes continuous then 30 min cool.
BA and GF maintenance manuals ( 71-00-00 :cool: ) show the same limits with an additional limit for compressor wash which is 2 mins on 10 off reapeated twice to wash. Then 2 on 10 off repeated twice to rinse. then 2 min on to dry then 30 mins off.
Both manuals also note that regardless of the wait period time between starts is also limited by zero N3 rotation which could well be more than the 1 min
The pilot and engineer limits seem pretty close to each other to me :D