Torques or T5's

[Steve76]

So... Hot day and the ol C30'ed S76 is struggling to pull the top off day old custard.

In the hover and due to a +10 and a +5 engine you have a substancial temperature split.

On the 'A' model do YOU choose to match the torques for takeoff or match the temperature.

Matching the temp's causes a 15%+ torque split and matching the temp's causes one engine to provide 20 - 30% more drive into the gearbox.

Is this accepted for the 'A' model? What do you do?
I know on the 'C' it was always to match the torques.
Thanks :cool:

[donut king]

I would say match temps....

Reason being..... 76A model limitations allow tq. on one engine to exceed 100% as long as the median tq. value between both engines does not exceed 100%( i.e... 105 + 95..... median is 100 obviously)

And given your engine spec's as an example..... your weaker spec'd engine requires 95tq to achieve 768 degrees, while the stronger engine allows 105tq to achieve 768.

I think!!!!!!!

Brain hurting.... everything getting blurry..... need sugar......more donuts!!!!!!!!!!!!

P.S. All this allowed as long as NR is within range.

Just my thinking.... hope it makes sense....correct me if I'm wrong!!


D.K

[Nigel Osborn]

After 24 years of flying the 76A, I've always found it best to match whichever limit reaches maximum first. So if TQs reach 100% while the T5s are low, so be it. If T5s reach 768 while the TQs are low, so be it. This way you have reached max power available without exceceing any limits.
With a C30, N1 should not get limited.

Hope Nick doesn't shoot me down!!:D :D

[helimutt]

Just from an engineers point of view (not helicopter eng.) I would have thought that the torque would be matched and not the temps. Matching the temps would make the gauges look nice and equal but the power developed would be more important?
Working on marine diesels where each cylinder produces up to 2500kw+, I adjust power and not temps to balance the engine as each unit is different. Is it not the case with turbines too? Just asking because I don't work on turbines (except steam ones)

[almost canadian]

I recall something of matching TQ blow 30 C ambient and T above that.....

[Nick Lappos]

Great question! I agree with Nigel, and generally match torque in cruise. For takeoff, match whatever is the limit to maximize the total power into the transmission (therefore, I usually match temp for takeoff on warm days, torque on cool days)

Generally, fuel burn rate matches torque, so you keep better fuel balance matching torques in cruise. But again, if you are up against the max cruise temp limit, and speed is what you want, then match temps and hold them both against the 694 cruise limit.

[Steve76]

Thankyou VERY much for all your thoughts.

Of course I take Nicks input as the next best thing to gospel, so matching T5 is the way to go.

I am glad it was a good question and I hope all involved picked up some tips.

Thanks again Nick and cheers to the rest of the lads...
Steve :D

[Rob_L]

Yet for the Dauphin the French use ng matching.

[GLSNightPilot]

I agree with matching whatever parameter is likely to be exceeded first. On the A++ it's often N1, so I tend to try to match N1 on takeoff, then match torque when in cruise, but on the A model T5 is likely to be the first limit, so I like to keep an eye on that. Most pilots I've flown with tend to match torques in cruise flight.