For a given turbine, Assuming the engine acceleration parameter is adjustable, Is the spool time inversely proportional with the probability for a flameout?

Just got a Merlin 160 but Im used to flying my Titan with a 5-6 second transition from idle to max RPM. I don't really need to take advantage of the extra fast acceleration..... Especially if it increases the chance of a flameout.

Pete

Pete, the acceleration setting of your Merlin 160 is set at a conservative value and is well within the engine capabilities without getting anywhere near the flameout threshhold.

So the short answer is no, setting a longer acceleration time will not make it any less suceptible to flameout, not that it is anyway

Rob.

Hi Pete, I don't know if there is a linear relationship between spool up time and probability of flame out, but they are related for sure.
Since I increased the spool up time of my engines, I have never had a flame out again.
I think that spool up time is more a marketing issue than a necessity. Just need proper throttle management.
I have also found very useful to have a throttle curve that gives you about 40% of throttle at 25% stick movement and 65% at 50% stick movement. This set up makes the throttle response more linear, and gives a faster response "feeling" during taxi and approach.

Jack

Hi! Jack; Hector from San Juan, Puerto Rico. You should place here the
throttle curve you published some time ago. I think I still have it, and been using it
since then. Very useful.


Hector

I had four flameouts in my supersport over about 75 flights.

After speaking to wren, and checked accel delays, it transpired mine was unusually low, (read stupidly low)

I then remembered someone trying to be helpful, had changed my accel delay at a jet meeting a couple of years ago to decrease the spool up time. (i honestly cant remember who)

I havent had a flame out since.

Reading the RCJI articles is seems that in high humid conditions reducing the acceleration times does have a bearing on flame out issues and smooth acceleration, but living in the UK I have never had the chance to test that. LOL

Mike

Pete,

I'm with Mike on this. I had to slow my P-70 down at Albany this year. It was hot and very humid. It didn't flame out, it just wouldn't accelerate. Just gurgled and choked. Dropped it down from Fast to Normal and she ran fine.

Bob

At altitude, here in Denver, I have to slow down the acceleration time on all my wrens when it gets around 90 deg or they will not take throttle.

Thanks for the input guys.. Meesh, I remember Mike telling me about your deal. Nice to have it sorted out. George, I sold my F-16 with a perfect running JC Falcon here on rcu to a gentleman in Denver. We were on the phone the first time he fired it up and it did not run right.

I've had to slow down my P-60 and later P60SE in hot and high situations. If you suspect the acceleration may be an issue, after start do a medium acceleration to full thrust, stabilize, then chop the throttle. Let it run for a few seconds at stabilized idle, then do a slam full throttle acceleration. If you are going to have trouble usually the quick slam acceleration after you have already allowed the engine to run through the full RPM range will show the flame out or compressor stall. In my particular Jetcats I've noticed trouble with acceleration flameouts are usually not a forward blowing flame from a traditional compressor stall but a big flame belch going aft from the tail pipe followed by the roll back flameout. It can be quite spectacular when you don't expect it, the first time. I didn't come up with this test routine, rather I had Bob Wilcox on the phone one day and I talked him through what I saw once and he had me run through a few tests and then we decided to slow the spool up and spool down onramp speed changes. Ran like a champ afterward. I have to say I was at 5000 feet and the density altitude that day was about 8500 feet. My Wren behaves exactly like the Jetcat, same solution. At sea level I'd be surprised if this would ever occur.