Menu Sign In Contact FAQ
Banner
Welcome to our forums

Aircraft performing below book numbers

Snoopy wrote:

The important aspects of the rule change are
- performance based fuel planning aka low cost airline lobbied for flying around with even less fuel

- that extra fuel is now not under the commander’s discretion anymore, and needs to be operationally justified. Conservative fuel planning comes under even more scrutiny.

Did the fuel regs change for CAT as well?

ESKC (Uppsala/Sundbro), Sweden

Yes they did.
But not yet all countries comply.
I know Ireland has introduced it already but Belgium hasn’t.
“Some airlines” weren’t ready yet.

The standard is still 5% contingency
If you want to deviate from that there need to be a statistical analysis of the fuel usage.

EBZW, Belgium

https://www.easa.europa.eu/en/newsroom-and-events/press-releases/easa-publishes-new-fuelenergy-rules-positive-environmental

The important aspects of the rule change are
- performance based fuel planning aka low cost airline lobbied for flying around with even less fuel
- that extra fuel is now not under the commander’s discretion anymore, and needs to be operationally justified. Conservative fuel planning comes under even more scrutiny.
It’s all in the name of cost savings and office farts pretending some „system“ or yet another „procedure in a manual“ will take care of it while in reality it exerts more pressure and scrutiny on pilots who are nudged to conform and fly around on fumes, and if something goes wrong the hypocritical question asked is „why didn’t you take more fuel?“.
And again the low cost black sheep freeload on everybody else who arrives with a couple minutes to spare. Because this „idea“ obviously doesn’t work in reality if everybody is low on fuel at the same time. So while others spend time in the hold burning €€€ others declare minimum fuel and get ahead.
So far I once landed after a 12 hour leg with final reserve remaining precisely at touchdown, and believe me, it’s stressful, when compared to the usual 6-8 tons, it’s only ~2. Feels like nothing. And when taking into account the accuracy of the gauges is ~1%, it might have been even less. Briefing to fly missed approach at low pitch up to keep the fuel flowing etc.
Reason was a re-routing and looooong low level TMA vectors (around the pitch black Everglades I may add).

always learning
LO__, Austria

Below book value, I don’t get there. But is it efficiency or is it top speed what is asked for when it is referred to “book values”?

My instructor asked me recently whether my fuel flow meter was bad, because it showed such a low fuel flow. We were doing some 130 indicated (140 knots true) showing constantly below 8 Gal/h. But it’s not so unusual for my Comanche. Today we did 130 true on less than 7 Gal/h. I’m doing instrument training, and we’re not in a hurry. In fact, it gets easier if you don’t need to rush. But yes, it can be flown quite economically…CHT was around 330, not too low I think.

Germany
Below book value, I don’t get there. But is it efficiency or is it top speed what is asked for when it is referred to “book values”?

My instructor asked me recently whether my fuel flow meter was bad, because it showed such a low fuel flow. We were doing some 130 indicated (140 knots true) showing constantly below 8 Gal/h. But it’s not so unusual for my Comanche. Today we did 130 true on less than 7 Gal/h. I’m doing instrument training, and we’re not in a hurry. In fact, it gets easier if you don’t need to rush. But yes, it can be flown quite economically…CHT was around 330, not too low I think.

I did encounter quite some aircraft during my flight career which were not performing ‘as of the book’, but every time something was really bad and when it was fixed it was back to ‘book numbers’. I learned from that to always check the numbers as they tend to be a really good early indicator for things to come. Your 130 on 8 sounds like typical VFR flying, so I guess that was what you instructor was referring to. When really doing IMC-IFR later, that ‘extreme eco’ flying will most probably become less pronounced … I noticed substantial changes in my flying habits when going from VFR to IFR and ‘avoid running on any extreme’ was one of them.

Germany

I‘ll bite: I don‘t think your FF instrument shows correctly. 130 KIAS, 140KTAS, is hardly possible on less than 8 GPH, in a Comanche. More like 10, maybe.

It’s very easy for the K-factor to be off a bit. I have seen lots of such aircraft. Have you validated your fuel totalizer totals against what you have refuelled after a flight? Ideally several times?

By the way, your airspeed indicator might well be off as well, after 50 years. I guess you only have one (steam gauge) ASI?

Last Edited by boscomantico at 28 Nov 17:45
Mainz (EDFZ) & Egelsbach (EDFE), Germany

UdoR wrote:

We were doing some 130 indicated (140 knots true) showing constantly below 8 Gal/h. But it’s not so unusual for my Comanche. Today we did 130 true on less than 7 Gal/h.

At what altitude?

This is a TIO540R?

So basically a IO540E with a Rajay Turbo?

I’d second @boscomantico, there is something wrong. 140 kts true at around 5000 ft requires roughly 55% power. According to the IO540E power setting table that goes at around 11.4 gph. 8 gph is below even 45% power. In fact, in the graph for the 540E, 8 gph is outside the tables in the POH of the non-turbo 260.

So either this is a different engine or I’d think your fuel flow may be off to the bad side.

LSZH(work) LSZF (GA base), Switzerland

boscomantico wrote:

By the way, your airspeed indicator might well be off as well, after 50 years. I guess you only have one (steam gauge) ASI?

That is something what worries me a little bit. On airplanes that have the AI replaced by a G5 I often see the speed indicated on the G5 differ from the original (kept in place) ASI. Which on is right? Is it the original one (because the G5 isn’t correctly calibrated), the G5 (because the original one got tired) or is it neither one? But then, the ASI will get checked at every annual, so the original should be correct.

EDQH, Germany

A G5 displaying IAS should be getting from an airdata computer module – a differential pressure sensor connected to the pitot and static tubing. That can be faulty.

For sure that speed at that fuel flow is impossible by some margin, on a 4-seat airframe.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

For sure that speed at that fuel flow is impossible by some margin, on a 4-seat airframe.

Mooney book numbers are actually slightly better than that, though one might argue about the number of seats.

EDQH, Germany
Sign in to add your message

Back to Top