As350 Slow Start

[Nomex]

Looking for ideas on possible cause for slow starts on a B2. All battery/electrics OK, NG drags between 20 & 32%. At sea level is noticeable but not too bad, but gets worse at altitude, to the point of almost not getting a start at 7000 ASL +. OAT doesn't seem to affect it, operating between 0 and 10c.

Thinking a FCU problem but just a guess.

Any thoughts?

 

[407 Driver]

The Solution to your problems.....

Of course, You'll inherit a whole bunch of "different" problems though ?

But seriously, I've never seen a bad 350 start. One of the BEST 350 engineers on-line is a shy young guy named Amadao, perhaps he can help you out....

 

[shaggy]

recently on a job with 2 BAs and one was having slow starts. engineers suspected fuel control after going through all of the other stuff such as the cable, temperature compensator, etc. i'm not an engineer though, and got crewed out before it was rectified and a/c went elsewhere.

 

[cyclic monkey]

Hi Nomex, I suspect you have tried advancing the throttle to get the T4 up into the yellow arc during the slow section. If it does not respond to this...you have a problem. It could be lots of things, with FCU high on the list. Get it fixed, it's not normal.

A little off-topic, but quite important.....
What does your engineer think it is, and what is your company doing to support his search for a solution ?????
Sorry to sound nosy, but why are you having to ask this here ??
I realise this forum is loaded with very experienced people, and it is a great place to come for help,.......but I would like to hear that your bosses are really trying to chase this snag for you. Good luck.

 

[Nomex]

I should have expected that one 407D.

Cyclic Monkey

A little off-topic, but quite important.....
What does your engineer think it is, and what is your company doing to support his search for a solution ?????
Sorry to sound nosy, but why are you having to ask this here ??
I realise this forum is loaded with very experienced people, and it is a great place to come for help,.......but I would like to hear that your bosses are really trying to chase this snag for you.

Just looking for some thoughts, ideas, similar experience which may help, since it is specifically at altitude when it is real slow, thought that indication may trigger a memory of a similar situation. Yes, something is not right with the start, they are doing FCU, acceleration checks etc. and will find the problem eventually. You also will be happy to hear the bosses are supporting the engineers chasing the snag - I'm just using the forum and the experience here to get a thought or two which may help out. Rest easy, the I'm not being abandoned - its not flying until it works - that's the way our company works.

 

[Nomex]

Cyclic Monkey

Yes, tried several methods including bring the TOT up during the slow period; holding the TOT at 600 until 20% then bring it up to the yellow arc;l slow steady advancing of the fuel control, etc.. nothing made a difference at all, thus the ???

tx anyway

 

[jetbox]

If I'm not mistaken, 20-30% is when the fuel is being transferred from the start nozzles to the injection wheel. (I haven't touched an Arriel in years so bear with me!) I've had this problem before a long time ago and I believe the problem was the pressurizing drain valve. This valve controls when the fuel transfers from the start nozzles to the fuel injection wheel and it was sticking just at that moment. The pilot had to advance the throttle almost all the way down just to start the friggin thing!!!!
Anyway, we were able to get a few components from Acro to trouble shoot the problem, at a cost of course!


P.S. 407 driver is right about Amadeo: excellent engineer if I say so myself. He was my apprentice many moons ago!!!!!!

 

[Underslung]

Here's a couple Ive seen in the past, cracked start nozzle fuel line, Acceleration bellows chamber full of water / ice -depending on OAT can freeze acceleration bellows in place and hang indefinetly. If the oring separating the high pressure fuel side is bad the cavity can also fill with fuel but you should be getting a fuel smell in the cabin as well, carry out P2 air chamber cleaning . The start fuel line cracks usually show up as slow until your into the injection wheel range, so basically if its hanging below 30% look at the nozzle lines or valve on the top of the stove. If slow above 30 check the acceleration bellows chamber. Hope this helps .
One of those engineers hiding in the background B)

 

[cyclic monkey]

Underslung, good post, welcome.

Nomex, it's good to hear you are getting good support from your company, and good suggestions here.

 

[skullcap]

Also may want to check your igniters for proper shimmingbut they should not be in the picture at this rpm. Also check for leak back to tank and the the a/c doesn't flameout when the starter is pushed once running. Had B2 give me grief at very high alt but always started right to 5000 meters. There is a procedure for advancing throttle up into emergency mode but that is telling you that the fcu is in need of tlc if it works but becareful when she does catch. Just a pilot's pov

sc

 

[sandy helmet]

If your problem gets worse with altitude it would most probably be your FCU - check the P2 capsule.

 

[skullcap]

I suppose they also have completed a permiability check on the sling ring(fuel injection manifold).

sc

 

[Nomex]

Tx for the input - the more suggestions the better. FCU & P2 were removed cleaned lubed etc, nothing obvious and no change in start, accel check same as before.

Not sure on your last skullcap & underslung, will check.
- as far as throttle position - not necessary to advance it past the normal spot to get the T4 up (ie: to emergency mode) - high T4 does nothing to help get it thru the 20-32%.
Also no fuel smell etc during the start.

 

[cyclic monkey]

Okay, I've figured it out !!! High T4 but still slow through 20-32%..............I've had this in Bell products too, but the problem solved itself much quicker than in an Astar.

My engineer said it was because there was only one tie-down strap that needed to reach the breaking point on the Bell products, as opposed to three on the Astar.

Have you checked this yet, Durex ??

 

[Nomex]

Cyclic Monkey

The tie-down comment was a good one and was taken in good humour, but the rest, seems a bit of a personal slight - I just shake my head, like a lot of other comments that are made by a few people on this forum. When someone posts a topic that is asking for advice, why do you have to make stupid comments, to people you don't know - I thought questions were encouraged - obviously you must know it all and look down at anyone who you presume has less knowledge & experience than you - you should be proud of yourself CM.

I appreciate the input from the rest of you. tx