Sikorsky S-76: Ask Nick Lappos

[Bright-Ling]

Which model has the steps which unfold automatically as the oleo is depressed?

[Ascend Charlie]

The same model that has the bar fridge door pop open as the gear flipper door pops shut.

[cpt]

S76 A++ engines match in flight.

One of our company's training captain insists we should match the fuel flow in cruise flight on our S76 A++, but the reasons he gives seems to be rather vague.
My common sense tells me to match the torques instead, and I would like to know others "76" fliers ideas and experience in that matter.
Thanks in advance!!!!
CPT

[donut king]

Hi CPT!

I don't recall any RFM limitation on this matter. Sounds more like an operational procedure than anything else..... i.e managing your fuel over the water to the rigs, maybe????

Any other info you can give.......reasoning from your training guy???

D.K

[tiebolt puller]

I thought you match on N1 on the Arriel 1S1. Matching fuel flow may give a torque split and difference in N1 due to engine condition.

[cpt]

Yes, I personnally believe that N1, T5, and fuel flow are significant of engine condition and providing they remain within their limitations, they can be mismatched.
In an another hand I have the feeling that the torques resulting from these figures reflect the output power to the gear box and therefore better deserve to be equally balanced.
Our training captain is indeed considering fuel managment first, but the split in fuel cunsumption is never that critical even on long sectors...
This issue is probably not essential since nothing about is in the flight manual, that's also why it is interresting to know others "S76 folks" opinions.

[S76Heavy]

On the A+ we match torques when we need the power, match N1s when it's hot and we need the power, and match FF in the cruise as far as it's practical.
If either match gives a large split in another parameter, we try and keep the split to something comfortable and have it checked after the flight.

We have no hard guidance on this, though.

[slgrossman]

I tend to agree with S76 Heavy. When operating near a limit match the engines in the parameter closest to its limit. In cruise I tend to match N1s, but don't see anything wrong with matching fuel flow. If matching engines in one parameter creates a significant split in another have maintenance check it out.

-Stan-

[GLSNightPilot]

I've never tried matching fuel flow, because it just doesn't seem that important. It's never that different in the aircraft I've flown anyway. I match torques in the winter, because that's the first limit I'll hit. In the summer, I match N1's, because that will be the first limit when it's hot. Most of the pilots I know tend to either match torques, or sometimes N1. I've never heard of anyone trying to match fuel flow.

[Aesir]

Don´t you S-76 guy´s have a limit on allowed torque split.
Its 4% in my B-222U.

[clearance]

I normally match N1's... (depending on size of the the Tq split)

You can always select fuel X-feed if/should you wish to fix the fuel imbalance

[trimpot]

I'm with you clearance

[RoamingCyclic]

I have a great deal of time on the A++ and have worked for 3 companies flying them. We always matched what ever would reach limits first at take off and matched torques during cruise.

I Agree with DK that there is really no reason for matching Fuel Flows. Given the reliabilty levels ( or lack there of ) of the Fuel Flow Indicators I see Very Little Merit In Teaching Line Guys To Match Them!

I guess at the end of the day we operate to what the company that pays our cheque wants us to do.

[rwm]

As an engine gets tired, it starts to burn more fuel, and more fuel means more ITT, EGT,ect. Also if your compressor starts to wear out, you start turning N1 faster to make up for loss of efficiency. Now if you start matching fuel flow on a miss matched airframe, you may end up worsening the condition of the engines. Now how exactly is the maintainers supose to fix a miss matched fuel flow? If you came and told me that your fuel flow was out, first thing I'd ask is what is your N1 and ITT.

[idle stop]

cpt:
Look in the Limitations section of the Flight Manual. You'll find limits for N1, Q and ITT but nothing, I recall, on Fuel Flow!
Balancing power input to the MGB is the most important parameter for airframe life. Matching N1 or ITT close to one engine limiting on those parameters may override this.

[Ascend Charlie]

In the B model with the PT6 and Fadec, we do not have to diddle with the trim switches, as the computer matches the chosen parameter for us.

And the choice is: Match Torque (to keep the input power to the gearbox balanced) or
Match T5.

No mention of N1 or fuel flow.

I can't see why you would attempt to match fuel flow. Even in a guzzler like the PT6 there is only a difference of 20 lb per hour at 75% Tq and 145 Kt.And the needle on the fuel flow gauge flickers more than 20lb anyway.

[engineoff]

Flying the straight C with the 1S1's it was company procedure to match N1's, which 95% of the time was the primary limiting factor, and simply accept the slight indifferance in fuel flow readings. The difference as A Charlie stated is really not likely to be significant...

Don't know how your regs differ over there Clearance but here in the UK we were prohibited from X-feeding during Public Transport ops except in the case of an emergency...

[cpt]

Thanks for all these posts !!! very interesting and technically enriching.
In our company too, we cannot balance fuel quantities in crossfeeding, and this procedure must be considered as an emergency procedure ( the flight manual also agrees with this, if I remember well).

[clearance]

engineoff -

Don't know how your regs differ over there Clearance but here in the UK we were prohibited from X-feeding during Public Transport ops except in the case of an emergency...

As per As per Flight Manual - Part 1 Section 1,
Fuel crossfeed operation is prohibited in flight except in strict accordance with the emergency procedure (page 3-2C).

Fuel crossfeed operations with vent line check valves (kit P / N 76070-30029-011) installed limited to:

Cat "A" - Emergency flight only
Cat "B" - Cruising flight only

We operate to Cat B.

Cheers
Clearance

[Nigel Osborn]

Clearance

Good to see you are still reading your flight manual! Must be all that good training you had!