Power Levers Mismatch on a Twin Eng Turboprop
Thread Starter
Join Date: Sep 2011
Location: Pakistan
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
Power Levers Mismatch on a Twin Eng Turboprop
Hi!
If any body can help me on this as i am new to Turboprop as maintenance incharge:
One of my aircraft (BN Islander with twin Allison 250 B17 engines) i found mismatch of power levers at takeoff torque value. Till groung idle, the difference is not much but as the power is increased the right (engine) power lever needs slightly more and more push ahead to get same torque as the left one.
At takeoff power the difference is too much for pilot to control both the power lever with one hand. The fuel flow rate of right engine is also higher than that of left engine.
If any body can help me on this as i am new to Turboprop as maintenance incharge:
One of my aircraft (BN Islander with twin Allison 250 B17 engines) i found mismatch of power levers at takeoff torque value. Till groung idle, the difference is not much but as the power is increased the right (engine) power lever needs slightly more and more push ahead to get same torque as the left one.
At takeoff power the difference is too much for pilot to control both the power lever with one hand. The fuel flow rate of right engine is also higher than that of left engine.
Would the AMM have something to say about this? A typical limit for throttle lever split seems to be one width of the power lever knob.
There may be tons of causes all through the system starting from a misrigging of the associated cables and likely not ending with some present or upcoming malfunction in the engine.
There may be tons of causes all through the system starting from a misrigging of the associated cables and likely not ending with some present or upcoming malfunction in the engine.
Thread Starter
Join Date: Sep 2011
Location: Pakistan
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
Hi Barit1!
rpm 2030 both engine torqu 830 lb TGT of offending engine is 50 degree more than its partner ie left engine TGT 750 and Right engine TGT 800 degree
rpm 2030 both engine torqu 830 lb TGT of offending engine is 50 degree more than its partner ie left engine TGT 750 and Right engine TGT 800 degree
Join Date: Feb 2002
Location: The Sandpit
Posts: 555
Likes: 0
Received 0 Likes
on
0 Posts
Hi Barit1!
rpm 2030 both engine torqu 830 lb TGT of offending engine is 50 degree more than its partner ie left engine TGT 750 and Right engine TGT 800 degree
rpm 2030 both engine torqu 830 lb TGT of offending engine is 50 degree more than its partner ie left engine TGT 750 and Right engine TGT 800 degree
If the rigging is correct and all the other parameters are the same but you have higher EGT (ITT/TGT) and fuel flow then you have a stuck bleed valve (either engine control or service bleed) OR some internal damage to the engine.
Either way, the engine is having to work harder to achieve the same power.
I hope you've grounded this a/c as throttle stagger that cannot be controlled single-handedly is a no no!
Thread Starter
Join Date: Sep 2011
Location: Pakistan
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
To all thanx for the helpful remarks!!
I got the problem solved. It was basically cordinator assembly whose setting was out and mismathed. By syncronising them, the power levers are now working fine at all power levels.
I got the problem solved. It was basically cordinator assembly whose setting was out and mismathed. By syncronising them, the power levers are now working fine at all power levels.
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
But are TGT's now matched more closely? If not, you still have work to do. Power assurance check is in order, otherwise RH engine may be redline limited on a hot/high TO.
Join Date: Oct 2010
Location: Germany
Age: 47
Posts: 402
Likes: 0
Received 0 Likes
on
0 Posts
relax gents, a small power lever mismatch is everyday business on every turboprop i have flown. on our two cheyennes in the company with pt6a engines everything - power lever position, ng speed , fuel flow and ITT are slightly different when matching the torque.
the torque gauge by itself may be a little erratic and show slightly wrong values.
no engine is like the other.
when asis ali managed to get them close together its a non event.
the torque gauge by itself may be a little erratic and show slightly wrong values.
no engine is like the other.
when asis ali managed to get them close together its a non event.
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
My point is - without a PA check, you don't really know how close to redline you will be on a hot day. Of course there's always some mismatch, but it's best to know just how much margin you have. Scheduled operators are required to monitor this.
