Aero Nerdery Thread (rotary-curious welcome)

[hscs]

Call Mx for the defuel truck. If not, fly, fly, and APU to kill 750 lbs per hour if you can’t take off based on not having your copilot ‘watch’ the fuel while you make a head call.

 

[Gatordev]

Why not turn on the APU and anti-ice?

This isn't for a -60, so I don't have those. I was using the -60 as an example of why my theory may hold water.

We left one engine in fly and the other at idle for an hour+.

I've done that before as well because I didn't want to risk not being able to start the engine back up. But my question is about burning MORE gas, not conserving gas.

So is your assumption that with one at fly and the other idle, that it’s burning more gas than both at fly? If I’m following you correctly, that doesn’t make sense to me.

This was always a HAC question for us, presumably because I came from a community where we only had a single spot to land on for blue water ops. If you flipped to your blue pages in the PCL, there were single-engine burn rates and max range speeds. The exercise that was taught was that if you're going to single up (in flight) to save gas, actually single up, don't just bring one engine to idle. The fuel burn (according to charts) would be higher with one at idle vs one shut down.

But...

I don't have the data to say if FLY/FLY at min power or FLY/IDLE is less efficient. IDLE is less efficient than FLY, but the FLY engine will be more efficient by itself than it would be sharing the ground load

And this is why I figured I'd ask. I don't have the education to understand the complexities of engine efficiency, let alone the difference at min power vs in flight. I'm just looking at it from a purely anecdotal point of view, watching what my engine instruments do. If both my Tq and TGT/TOTs go up on an engine, it would seem that means it has to burn more fuel than it was before. I totally understand load sharing makes can make it more complicated, I just can't prove how with the limits of my available instrumentation.

 

[hscs]

Maybe a thought experiment - in the 60 with one in fly and other in idle, look at the torque values. Very vague memory but would say one was around 40% and another low double digits. Compare that number with both engines at fly. Think I remember around 20%.

Sum both, and see how they compare. That might give the answer.

 

[insanebikerboy]

This was always a HAC question for us, presumably because I came from a community where we only had a single spot to land on for blue water ops. If you flipped to your blue pages in the PCL, there were single-engine burn rates and max range speeds. The exercise that was taught was that if you're going to single up (in flight) to save gas, actually single up, don't just bring one engine to idle. The fuel burn (according to charts) would be higher with one at idle vs one shut down.

Yeah, I remember that HAC question too. Singling up saved gas because at bucket speed the remaining engine doesn’t burn exactly twice the amount of gas as with two motors on.

I may have misinterpreted your question but my point was if you wanted to burn gas it’d likely be better to have both at fly and apu and anti ice on. Well, no apu in your current aircraft.

 

[ChuckMK23]

Well, no apu in your current aircraft.

EC135 still?

 

[Gatordev]

EC135 still?

Correct.

Maybe a thought experiment - in the 60 with one in fly and other in idle, look at the torque values. Very vague memory but would say one was around 40% and another low double digits. Compare that number with both engines at fly. Think I remember around 20%.

I've done this in the -135 (and your -60 numbers sound correct), which is why I'm thinking my theory is correct. Another thing to keep in mind is most civilian helicopters are designed to run at idle, unlike the -60 where the head is fairly unstable at idle.

That said, as far as numbers... with both at idle, you get ~15% Tq each and some TOT (I can't remember off the top of my head). With one in fly, you get ~30% and 0%, with the one in fly having a higher TOT. I need to check to see if TOT stays the same when the other one goes to 0% Tq (+/- a little).

Part of the problem is when I actually need to do this to lose weight, I'm also doing at least 3 other things (setting up a headset for my pax, talking to Ops, diddling with the iPad to set my manifest up correctly, etc) so I can't fully direct my attention to the less than precise fuel gauge and the clock.

Singling up saved gas because at bucket speed the remaining engine doesn’t burn exactly twice the amount of gas as with two motors on.

It also worked at Max Range, which was shown on that chart as well.

and anti ice on

Dumb question...does turning the anti-ice on in the -60 on the ground even do anything? The valves are already open and the inlet anti-ice shouldn't turn on if it's warm enough. I can't remember if the TGT goes up on the ground or not...it's been too long.


Either way, no anti-ice on the -135, so no help there.