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HeliTorque :: View topic - JetRanger 'Hot starts.'
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HeliTorque Forum Index » Flight Dynamics

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Copterfan
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PostPosted: Fri Mar 24, 2006 4:40 pm    Post subject: JetRanger 'Hot starts.' Reply with quote

I'm starting to feel the love for the Jr, but in virtually everything I read about it, especially if compared to say the R-44, the threat of hot starts is mentioned.

But: What are they, how do they happen, and why do they happen just to the JR?

If I bought one, would I have to expect one, and would I know if the aircraft I bought had had one?

I can't find any technical info about this phenomenon, but it is usually mentioned in anything about Jr's, so I thought I'd ask.

Apologies if this is really basic, I just don't know what it is. Confused

Cheers in advance,

Copterfan.
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heliaviator
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PostPosted: Fri Mar 24, 2006 5:02 pm    Post subject: Reply with quote

WEEKEND WARIER HAS A TIDY 206BIII
I'M SURE HE WOULD OBLIGE WITH SOME INFO.
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BigMike
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PostPosted: Fri Mar 24, 2006 5:30 pm    Post subject: Reply with quote

Hi there Copterfan. A Hot Start is an exceedence in temperature when starting. Simple really.
Basically the TOT, or Turbine Outlet Temperature, becomes too hot and can cause damage to the engine. The hotter, the larger the repair bill!
They normally happen due to a low battery. They will NOT happen if the pilot is paying attention!
A basic start involves spinning the turbine up via the start button, then introducing fuel with the throttle. If you do not have enough engine speed, ie cold air coming through, then the fuel will ignite and it will very quickly become too hot in the engine. You also need plenty of power in the battery for it to reach a "self sustaining" speed where it no longer needs the starter motor spinning, to keep things happening. This is a VERY basic discription of the procedure Wink
Cure? simply close the throttle and keep your finger on the starter until the Temp drops below 150.

If you do a type rating, all will be explained.
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PostPosted: Fri Mar 24, 2006 5:52 pm    Post subject: Reply with quote

ah ha.....that explains the thread elsewhere about disconnecting EC120 batteries when left overnight as they tend to drain quickly
Bit much when you spend
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PostPosted: Fri Mar 24, 2006 7:41 pm    Post subject: Reply with quote

.

Last edited by weekend warrior on Wed Jun 07, 2006 9:25 pm; edited 1 time in total
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KBayDog
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PostPosted: Fri Mar 24, 2006 8:34 pm    Post subject: Reply with quote

If you have access to one, an external power supply will get the starter up to speed a lot sooner than a battery. The N1 will be at and above 15% before you know it, and the turbine temperature will be much, much lower after lightoff. (Ensure you get the twist grip open as soon after 15% as you can.) The external power will also get the N1 turbines up to 58% quite a bit quicker than with a battery start. This will also allow (and require) the starter and ignitor to be engaged for a much shorter period.
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PostPosted: Fri Mar 24, 2006 9:40 pm    Post subject: Reply with quote

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Last edited by weekend warrior on Wed Jun 07, 2006 9:25 pm; edited 1 time in total
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PostPosted: Fri Mar 24, 2006 9:58 pm    Post subject: Reply with quote

Thanks guys, amazing responses, as usual. Very Happy

Heliaviator;
thanks for the reference, and didn't WW come up with the goods? Very Happy I too followed the Ec120 thread, and came to the same conclusion about the money, especially with all the other niggly things that required expensive maintenance. Smile

Bigmike;
Hello back, and thanks for the great answer. It's good to know that it's the nut behind the cyclic that's at fault and not the helicopter. Wink

KbayDog;
thanks for this great tip, I will certainly remember it and consider it as part of the costs.

WW:

Wow, what another amazing answer with diagrams and photo's too. You excel yourself as usual, thank you. Cool

OK; the reason I'm asking this question is that I am re-considering my training options (thanks for the great help you've already given me on this point WW Wink ). I went to Heli2000 t'other day and had a good look at the R-44 II. I joined in with a chap who was type-converting from R-22 to R-44 (on the A-check). R-44 is lovely and flies very neatly, but I was amazed how much the tail boom shook when the rotors were winding down. Surprised

After considering costs, and my turbine ambitions, and my plans for next year too; I came to the conclusion that it would be better, or should I say, more cost effective long-term, to do it on the B206. I know WW that this was your initial advice and conclusion, feel free to regale me with howls of derisive laughter... Embarassed Embarassed Embarassed

So, having been round the Mulberry bush at least twice, I feel I have a workable plan. Wink

WW; could I send you a .pdf of an aircraft I have found for sale? I think that I have a basic idea of hours, years, cost, equipment etc. But I wondered if you could just look and see if the aircraft is, at all ballpark Wink ?
BTW; I didn't pm you initially because I didn't just want to bombard just you with questions. Wink

Thanks again all of you,

Cheers,

Copterfan.
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PostPosted: Fri Mar 24, 2006 10:29 pm    Post subject: Reply with quote

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Last edited by weekend warrior on Wed Jun 07, 2006 9:25 pm; edited 1 time in total
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PostPosted: Fri Mar 24, 2006 10:50 pm    Post subject: Reply with quote

weekend warrior wrote:
Hot starts can happen just as easily with external power.


Very true.

Good point about the condition/output of the external power...it hammers home the point that you always need to be ready to close the twist grip.
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PostPosted: Sat Mar 25, 2006 10:39 am    Post subject: Reply with quote

With regards to the term "Hot Start" WW is refering to a start that is warmer than normal. A Hot Start generally refers to an exceedence.
You will find that the engine is almost self-sustaining at about 46% N1 onwards. Have a look next time you do a start and watch the TOT drop away at about this point(but don't take your finger off the starter!!)
If you think you Ex-power is a bit low then keep the battery switch on as well to help.
The best start is one that is quick, with the temp around 800. Don't get fixated on reaching 15%. If you hear it starting to "hang" another words that is as much as you will get out of it, then light it off. Remember you still need some power to get it self-sustaining. You can light it off at 12% depending on the outside temp, just make sure that if you do a start not long after a shut down, make sure it is below 150 before lighting it off.
The more you do, the more you start to get a feel for it.
BUT, don't ever think it will always be normal.

I have been caught out by a stuck throttle cable, where after a compressor rinse, and pushing the ignitor CB in, it immediately lit off (throttle still closed!) and I watched as it raced up to 890, hung then slowly dropped below 810.
What ever happens, KEEP YOUR FINGER ON THAT STARTER BUTTON Wink
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PostPosted: Sat Mar 25, 2006 10:39 am    Post subject: Reply with quote

Copterfan wrote:
R-44 is lovely and flies very neatly, but I was amazed how much the tail boom shook when the rotors were winding down. Surprised


Don't be put off by that - firstly they'll not all be the same. Secondly, if you (sensibly*) play with the pedals a bit, you'll eliminate some of that wobbling. Largely caused by the tail rotor still moving air around.

The main rotor too will cause wobbling, again just gently adjusting the cyclic can alleviate it.

(Sensibly in the case is don't put it to the extremes at relatively high rotor speeds...! Shocked
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PostPosted: Sat Mar 25, 2006 1:06 pm    Post subject: Reply with quote

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Last edited by weekend warrior on Wed Jun 07, 2006 9:26 pm; edited 1 time in total
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PostPosted: Sat Mar 25, 2006 5:25 pm    Post subject: Reply with quote

WW, warmer than normal is what I thought you meant as you said you had 6 Hot Starts in 1 day. I can understand 1 off a weak battery, then another off a low GPU, but then 4 more? from the same GPU? or from 4 different one's?

Which model 206 dosn't let you start with the battery on?

Not extracting the Michael mate, just interested Wink
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PostPosted: Sat Mar 25, 2006 5:44 pm    Post subject: Reply with quote

That'll be a B-somethingelse with more than one engine that Wozza's referring to... Wink
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