"Cracking" the throttle
I know the feeling, happened to me once while instructing in 206. The guy had about 30 hrs in turbine and I would say that in every single flight lesson I told him to stay on the starter ´till 58%Ng.
Well this time he let go, but at about 30%. Seems she was already under self sustained start/run by then because the temp didn´t really seem to increase any for the fraction of the second it took me to hit the start button. I always keep my right hand on the collective, with my thumb resting on the collective switch panel (can you say that for B206, not that many switches there!) when instructing.
Sure was scary, but what impressed me was that there was no apparent temp rise.
Bendix, gotta love it : )
Well this time he let go, but at about 30%. Seems she was already under self sustained start/run by then because the temp didn´t really seem to increase any for the fraction of the second it took me to hit the start button. I always keep my right hand on the collective, with my thumb resting on the collective switch panel (can you say that for B206, not that many switches there!) when instructing.
Sure was scary, but what impressed me was that there was no apparent temp rise.
Bendix, gotta love it : )
When you had that finger off the starter button, and the TOT didn't rise that much, what was the air temperature?
On a normal start, say air temp. 30°C, i've seen that needle coming close to 820, very close. I had already started the 10 sec countdown, but then it all came to normal. I have a bad feeling about that finger off on a hot day.
On a normal start, say air temp. 30°C, i've seen that needle coming close to 820, very close. I had already started the 10 sec countdown, but then it all came to normal. I have a bad feeling about that finger off on a hot day.
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hey all, rotor Dog is right, relax, crack it a little way past the stop pull it back then depress the stop, all before its passing through 500deg or so.
Regards to letting go the starter on a 40 degree day, cant say i notice any difference, always other variables, think its been over a year or so sinse the last and then 2 in 3 days! i know some instructors who say "keep finger over the idle stop incase" B***** hold it down, do a dry run and snap the throttle against the stop and see how hard it is to press it, ALL over by then!! i think this is the most important bit to me,
Regards to letting go the starter on a 40 degree day, cant say i notice any difference, always other variables, think its been over a year or so sinse the last and then 2 in 3 days! i know some instructors who say "keep finger over the idle stop incase" B***** hold it down, do a dry run and snap the throttle against the stop and see how hard it is to press it, ALL over by then!! i think this is the most important bit to me,
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Gomer Pylot:
Who, me? Really, really busy? Nope. If you know how your ship starts, and if it's been starting consistently, then there is nothing to it. In a 206B, I merely open the throttle to...wherever. The engine lights off normally. As the start progresses, I just make sure that the throttle is back to the stop. No drama at all.
As far as releasing the starter button early...I know that the book says to hold the starter to 58%, but I also know from experimentation that a C-20B is self-sustaining from about 45% N1 up (depending). Releasing the button early (like between 20 and 30%) is not disastrous, and the TOT does not spike upward like a fuel control gone bad (although you do have to be quick to get the button back down). That compressor puts out quite a lot of cooling air. In fact, a C-30 compressor is so powerful that if you wait until too high an N1 to introduce fuel you might not even get it to light off.
Pilots do get anxious during a turbine start. But if you have your procedures down pat and you don't have your head up your arse, it's really no big deal. (On the other hand, if student starts a no-flywheel piston-engine ship like an Enstrom with the throttle open a little too much...watch out!)
I'll bet you got really, really busy really, really quickly. For all the good it did you, huh?
As far as releasing the starter button early...I know that the book says to hold the starter to 58%, but I also know from experimentation that a C-20B is self-sustaining from about 45% N1 up (depending). Releasing the button early (like between 20 and 30%) is not disastrous, and the TOT does not spike upward like a fuel control gone bad (although you do have to be quick to get the button back down). That compressor puts out quite a lot of cooling air. In fact, a C-30 compressor is so powerful that if you wait until too high an N1 to introduce fuel you might not even get it to light off.
Pilots do get anxious during a turbine start. But if you have your procedures down pat and you don't have your head up your arse, it's really no big deal. (On the other hand, if student starts a no-flywheel piston-engine ship like an Enstrom with the throttle open a little too much...watch out!)
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Bendix system question
Can anyone tell me how much modulation on a Bendix is available on start up.
On a 206 B2 start with a newly tuned Bendix, I cracked the throttle to idle detent and the temp quickly raced into the high 800's. This has never happened on this machine before. Throttle had to be wound back until flame-out to reduce TOT.
The question is: Is there any modulation available while closing the throttle, or is flaming out the engine the only way to reduce TOT?
Any help appreciated.
Ax
On a 206 B2 start with a newly tuned Bendix, I cracked the throttle to idle detent and the temp quickly raced into the high 800's. This has never happened on this machine before. Throttle had to be wound back until flame-out to reduce TOT.
The question is: Is there any modulation available while closing the throttle, or is flaming out the engine the only way to reduce TOT?
Any help appreciated.
Ax
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There is no modulation available for the Bendix system installed on 250-C20 series engines. The CECO systems used on 206BII ships had this feature.
With the Bendix system, if it is going hot, all you can do is cut the throttle, and then either charge the battery, hook up an APU, or adjust the fuel control.
The Bendix fuel control has two adjustments for the start cycle on a C20. A derichment adjustment (effects temps between 0 and 30 percent N1) and the tweeker (adjusts entire start cycle).
If you are going hot at the beginning of the start cycle, you need to adjust the derichment down.
If you are stagnating around 40 to 50 percent N1, you need to go up one click on the tweeker, and turn down the start derichment.
Bendix did upgrade their systems on the 250-C28 and 250-C-30 series engines to include modulation during start cycles.
If you can get a 206BII flight manual, there will be two start procedures available for the options (Bendix vs. CECO).
With the Bendix system, if it is going hot, all you can do is cut the throttle, and then either charge the battery, hook up an APU, or adjust the fuel control.
The Bendix fuel control has two adjustments for the start cycle on a C20. A derichment adjustment (effects temps between 0 and 30 percent N1) and the tweeker (adjusts entire start cycle).
If you are going hot at the beginning of the start cycle, you need to adjust the derichment down.
If you are stagnating around 40 to 50 percent N1, you need to go up one click on the tweeker, and turn down the start derichment.
Bendix did upgrade their systems on the 250-C28 and 250-C-30 series engines to include modulation during start cycles.
If you can get a 206BII flight manual, there will be two start procedures available for the options (Bendix vs. CECO).
Last edited by rotormatic; 26th Oct 2005 at 04:15.
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I would say it is much easier to pick a delayed start on a bendix. 15% n1 crack the throttle count 1000 2000 3000 then crap yourself and close the throttle if it hasn't lit off. Where as on a c30 modulated start you tend to keep opening the throttle a little bit more and a little bit more until whooomp then you crap yourself and close the throttle.
Engine starting
In the same vein, what is the start procedure for a MD Explorer? I understand this has FADEC? could someone explain the advantages/disadvantages of this system.
Thanks
Thanks
Start sequence on an Explorer?
From memory:
- Walk (never run - it frightens the bobbies) to aircraft, open door, switch battery master on.
- Put "cooker switch" for required engine to "IDLE"
- Climb in/ strap-in while watching the FADEC do its thing.
- Put second engine's cooker switch to "IDLE" - watch the IIDS as FADEC does it all.
- Do all the other role equipment checks, wait for second bobby to join you on board, switches to "FLIGHT" and you're ready.
Best engine start system I've ever used - beats the Arrius 135 with its weird FADEC switches any day.
From memory:
- Walk (never run - it frightens the bobbies) to aircraft, open door, switch battery master on.
- Put "cooker switch" for required engine to "IDLE"
- Climb in/ strap-in while watching the FADEC do its thing.
- Put second engine's cooker switch to "IDLE" - watch the IIDS as FADEC does it all.
- Do all the other role equipment checks, wait for second bobby to join you on board, switches to "FLIGHT" and you're ready.
Best engine start system I've ever used - beats the Arrius 135 with its weird FADEC switches any day.
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Are there any videos available for us novices to watch the correct start procedure for a turbine engine (B206). If so can someone please post a link to it. Sounds like to me thats why they invented FADEC to stop this from happening and make the starting a turbine fully automated. Might save on the cost of a cooked engine.
John
John
Big Johnno:
I'm not aware of any video. Starting a 206 isn't rocket science.
If you're worried about cooking an engine, then I'd recommend two things:
1. Get a decent conversion course with a reputable instructor, express your concerns, get a very thorough brief he'll watch you on your first few starts anyhow.
2. Go through lots of dry runs / touch drills in the seat, practising different scenarios and what you'd do in each case.
And always run through what you're planning to do before every start - things happen quite predictably in most cases and it's a question of being prepared for the abnormal.
I'm not aware of any video. Starting a 206 isn't rocket science.
If you're worried about cooking an engine, then I'd recommend two things:
1. Get a decent conversion course with a reputable instructor, express your concerns, get a very thorough brief he'll watch you on your first few starts anyhow.
2. Go through lots of dry runs / touch drills in the seat, practising different scenarios and what you'd do in each case.
And always run through what you're planning to do before every start - things happen quite predictably in most cases and it's a question of being prepared for the abnormal.
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As the man says, it isn't rocket science, but it can be intimidating when it's your first turbine. I can offer this:
"The best position to leave the blades in is actually around 30° from the longitudinal axis. You have a lot to look at when you start the engine, and one of the checks is to ensure that the blades are turning by 25% gas producer RPM. This actually happens at around the time of the first TOT peak, by which time, if the blades are set as described, they should be moving into your peripheral vision and you don’t need to take your eyes away from the TOT gauge. If they were at 90°, you wouldn’t see them until the gas producer was well over 25%, without taking your eyes away from the panel. If you put the blades fore-and-aft, there is a slight risk of exhaust gases scorching the underside of a blade, and you wouldn’t be really sure that you had untied the blades anyway."
Although the Bendix doesn't allow modulation, you can get a cooler start by watching the fuel pressure and stop opening the throttle when you see the needle flicker. Be prepared to wait a second or so for light off.
With regard to N1 RPM, don't wait until the engine rotation peaks, because you will be wasting battery power that will be needed later. The Allison book says you can open the throttle at around 13%, provided the engine is accelerating. However, you still need to be careful of a weak battery, which you can get an indication of by listening to how the igniter snaps. Better still, use external power.
One Most Important routine to get used to - if you think you are going to have a hot start, close the throttle first. Don't take your finger off the starter until you are sure the TOT will not go any higher
Phil
"The best position to leave the blades in is actually around 30° from the longitudinal axis. You have a lot to look at when you start the engine, and one of the checks is to ensure that the blades are turning by 25% gas producer RPM. This actually happens at around the time of the first TOT peak, by which time, if the blades are set as described, they should be moving into your peripheral vision and you don’t need to take your eyes away from the TOT gauge. If they were at 90°, you wouldn’t see them until the gas producer was well over 25%, without taking your eyes away from the panel. If you put the blades fore-and-aft, there is a slight risk of exhaust gases scorching the underside of a blade, and you wouldn’t be really sure that you had untied the blades anyway."
Although the Bendix doesn't allow modulation, you can get a cooler start by watching the fuel pressure and stop opening the throttle when you see the needle flicker. Be prepared to wait a second or so for light off.
With regard to N1 RPM, don't wait until the engine rotation peaks, because you will be wasting battery power that will be needed later. The Allison book says you can open the throttle at around 13%, provided the engine is accelerating. However, you still need to be careful of a weak battery, which you can get an indication of by listening to how the igniter snaps. Better still, use external power.
One Most Important routine to get used to - if you think you are going to have a hot start, close the throttle first. Don't take your finger off the starter until you are sure the TOT will not go any higher
Phil
I forgot one thing.
Remember BITT - Brake off, Igniters In, Tiedowns off / Throttle closed - or some other regular form of check which makes sure that BEFORE you finally commit to pressing the tit, everything is ready to go.
No I didn't, I forgot two things.
Make sure you don't hold the throttle closed hard against the idle stop - you won't be able to press the button and close the throttle if you do.
Remember BITT - Brake off, Igniters In, Tiedowns off / Throttle closed - or some other regular form of check which makes sure that BEFORE you finally commit to pressing the tit, everything is ready to go.
No I didn't, I forgot two things.
Make sure you don't hold the throttle closed hard against the idle stop - you won't be able to press the button and close the throttle if you do.
