Turbine RotorWay

David Stewart's Ship
March 2003

John Spurlings Turbine RotorWay

2003

2004

2004

 
As more and more Jet Execs are being completed I thought that a few insights might be appreciated. I just returned from instructing two students in Jake Henke's new Jet Exec that Steve Walton recently completed for him. These are really nice ships to fly with a few cautions.
 
I have now instructed and given transition training in 2 different Jet Execs to 3 students and have found that there are a few diffences that bear noting.

The most obvious is the engine starting procedure. You need to be very watchful to insure that you do not get a hot start that can burn up your turbine in a matter of seconds. I found that the following sequence worked the best and we had smooth starts every time.
 

Depress the starter button and wait until you hear the burner ignite, engage the governor switch but keep your hand on it to be able to rapidly turn it off should a hot start occur. While depressing the starter watch the engine RPM increase to around 56% and then release the starter. The governor is set for around 52% RPM with the trottle rolled to idle so when the starter is released the engine smoothly settles down to the 52% setting. Initially we were releasing the starter at around 52% and the governor would immediatly give a shot of fuel that would momentarily cause the engine to flutter and the EGT to dramatically rise. This was the start of a hot start. We found that the 56% method worked perfectly every time
 
More later if anyone is interested. I don't want to ramble if no one is getting the benefit or entertainlment value from this. Let me know if anyone is interested in hearing more.
 
Orv Neisingh R/H CFI 

Is there anyone out there that has enough experience with the small turbine that is used on the Jet Exec to lend some insight to what I have experinced.
 
When I began an auto in the Jet Exec I did so very smoothly and with very little roll off of the throttle the first time to see how the turbine would act. Just after needle separation the engine began to surge and hunt causing the nose of the helicopter to yaw back and forth to the sides. This was a bit unnerving as it makes me wonder what the engine would do if the pilot performing the practive auto rolled off just a little to much throttle and then during the recovery applied it too rapidly.
 
The reason I question this is that during the initial run up and sprague clutch check when the throttle is rolled down to gain the expected needle separation, if the throttle is then rolled back to full where it belongs, the governor evidently applied too much fuel and the engine sounds like it is flaming out. This would not be a good response from the engine at the point that you need it to recover from a practice auto, it would turn it into a full down auto and the CG of that engine/trans. is quite high, ie. possible rollover at ground contact.
 
If anyone has some insight on a remedy or their own experinece, I would love to hear it. 
 
Orv 

 From: Orv Sent: 7/20/2004 6:32 PM 

At Homers I finally had the pleasure of meeting Russ Garish and chat with him about doing autos in the Jet Exec. He agrees with me that it is best not to do them right now until a definitive solution to the above problems is found. He also suggests that we practice the autos in the R22 or the piston Exec because we know that the engine will be there when we roll the throttle back on.

 Orv Neisingh Helicopter CFI

 
Orv, It was a real pleasure meeting you after all the years of e-mailing.  You are indeed an icon in the instructing field.
 
As we discussed, yes, lets confine autos to the piston Exec for now.  If a JetExec owner has to do a for-real auto, just do it the same way as in the piston.   I am confident it is just a matter of adjusting the governor and fuel control so it will not try to accelerate after needle split.   Mine does not do the surging you describe.   Another local high time instructor and JetExec owner has agreed to work with me to develop a set of procedures.   We will be doing this in August-September.
 
I am also going to install a different type of servo motor, to see if that is more stable.
 
Russ

 
Russ, I.m sorry I couldn't make it to Homers this year I really would have 
liked to meet you in person.
but I had to finish up the ship for Tom Olsen.I now have the new splined 
shaft and Hardy disc mods done and have test flown and all is smooth (So 
Far).

As far as Auto's are concerned , you can still do full down collective
without splitting the needles and get a pretty good idea of how the ship 
performs,and still practice your flairs so you can get an idea what they 
feel like in a real Auto.IMHO

Regards

Steve

From: Amosharlev Sent: 7/21/2004 6:40 AM 

Apologizing for interrupting, If I my add,  SAFETY WISE, be vary careful for Rotor RPM go high during auto. As it can lead to engine cut, again unfortunately I am not familiar with Jet exec but on single engine Jet engine helicopters over RPM during auto, can lead to engine cut basically as governor is in extreme low fuel while RPM is way high

From: Russ Gerrish Sent: 7/22/2004 1:01 PM 

Dear Amosharlev, 

Sorry I don't know your real name. 

The systems in the JetExec are separate, so the circumstances for engine cut (overspeed) should never happen.  The governor is only controlled by engine speed and there is no input of rotor rpm.  On needle split, the sprag clutch slips, so what the governor will do is maintain the engine speed as dictated by the throttle twist grip (potentiometer) position (normally 90% in a practice auto) and turbine speed sensor.  In other words, there is no interconnection between rotor speed and the engine overspeed circuit.   All that should happen if the rotor rpm goes up to, say 110%, is the sprag should slip more but the engine speed should stay at 90%.

Thanks for your concern.

Russ 

END