RR/Allison 250 series temperatures while starting
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RR/Allison 250 series temperatures while starting
Legend tells of a letter or guidance issued by either RR or Allison eluding to the engine manufacturer's preference to the engine being started quite warm.
My first run in with this tale was about 10 or so years ago when I hopped in a jetranger with the DO of a company I just contracted onto for an interview flight. Hit the starter and opened the throttle at the appropriate time. Engine temperature skyrockted well past the redline of the gauge and was gunning for the 927 dot. I aborted the start. He asked my why I gave up so early then explained that all of the company's 250C20 series engines (Probably 10-15 helicopters) were set to start that warm as Rolls Royce put out some sort of guidance. I started the helicopter again and again the temperature headed to the 927 dot with no delay. Stopping just a fraction of an inch short and then very quickly falling back out of the 10 second range for starting above red line.
Sure enough every single tail number I flew for them with a c20 started the same way.
I've heard of this letter more than once since then.
Does it exist? Can someone post it? Where can I download it?
My first run in with this tale was about 10 or so years ago when I hopped in a jetranger with the DO of a company I just contracted onto for an interview flight. Hit the starter and opened the throttle at the appropriate time. Engine temperature skyrockted well past the redline of the gauge and was gunning for the 927 dot. I aborted the start. He asked my why I gave up so early then explained that all of the company's 250C20 series engines (Probably 10-15 helicopters) were set to start that warm as Rolls Royce put out some sort of guidance. I started the helicopter again and again the temperature headed to the 927 dot with no delay. Stopping just a fraction of an inch short and then very quickly falling back out of the 10 second range for starting above red line.
Sure enough every single tail number I flew for them with a c20 started the same way.
I've heard of this letter more than once since then.
Does it exist? Can someone post it? Where can I download it?
The engineers I have spoken to, since my first C250 start in 1980, said that a hot and fast start was the way to do it. However, "rocketing towards 927" was not the way it happened for me. More a gentle cruise into the yellow, start counting, and usually back below yellow by 5 or 6.
Join Date: Oct 2006
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This could possibly be it. It's a now deleted commercial service letter (I think 3049).
https://www.scribd.com/document/3641...r-C20-and-C20R
This link has a link that lets you download the entire letter in a PDF.
https://www.helikopterfliegen.de/for...?showtopic=834
https://www.scribd.com/document/3641...r-C20-and-C20R
This link has a link that lets you download the entire letter in a PDF.
https://www.helikopterfliegen.de/for...?showtopic=834
Last edited by helonorth; 1st Jul 2021 at 00:26.
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The B206 could be fitted with a Ceco or Bendix FCU my failing memory recalls. Bendix gave very easy controllable ITT rise, Ceco scared the pants off you with its rapid rise and seeming lack of control. C20 in the 76A was a dream to start.
Megan, the Chandler-Evans (CECO) was a modulated start, not an automatic start like the Bendix. If it gets hot, back off a smidge. But you can't snap it to idle like the Bendix, as I'm sure you now remember.
Only hot starts were with a sick battery, or after it sat in the snow at Charlotte's Pass for 3 days, the engine froze solid, starter made no progress at all. Couple of hours with a Tangi on the end of 3 extension cords loosened it enough to turn over.
Only hot starts were with a sick battery, or after it sat in the snow at Charlotte's Pass for 3 days, the engine froze solid, starter made no progress at all. Couple of hours with a Tangi on the end of 3 extension cords loosened it enough to turn over.
206 was 44 years ago, 76A slip of the fat finger.
If the temp was ’rocketing’ toward 927 in any B17 I have started I would be concerned for sure. I abort such starts, motor and try again. The RR manual sys ANY exceedance is a hot section OH these days, not just an inspection. With modern recording EMS an exceedance of 1/2 a degree for a second (sampling time) is worth about 100k as it’s on the USB download in black and white. I have stopped starts with only a couple of degrees margin, all good, but don’t take the chance if it’s getting hot very quick.
if one is familiar with individual engines is a bit easier to tell if it is behaving ‘normally’ also.
im always wary of first start after any major maintenance, and listening to the starting light off/ acceleration exhaust tones often tells if there is an issue about to raise its head.
I am familiar with the Service Letter, and it does make sense, it’s just a bit scary sometimes.
if one is familiar with individual engines is a bit easier to tell if it is behaving ‘normally’ also.
im always wary of first start after any major maintenance, and listening to the starting light off/ acceleration exhaust tones often tells if there is an issue about to raise its head.
I am familiar with the Service Letter, and it does make sense, it’s just a bit scary sometimes.
