Fuel reserve Turbine / Piston
 

Does anyone know why the final reserve is 30 minutes for IFR in a turbine aircraft (or in day VFR) while it is 45 minutes for IFR in a piston aircraft (or in night VFR).
This difference is independent of the number of engines, number of crew members, speed of the aircraft, etc.
I fail to understand what makes the situation of an out-of-fuel piston aircraft more critical than the situation of an out-of-fuel turbine aircraft.

Luc I'm making a guess but a turbine powered aircraft would be faster than a piston engined aircraft

Is it to do with the fact that turbine aircraft tend to have more accurate fuel gauges?

Fookinell!

ICAO Annex 6 states:
"1) for a reciprocating engine aeroplane, the amount of fuel required to fly for 45 minutes, under speed and altitude conditions specified by the State of the Operator; or
2) for a turbine-engined aeroplane, the amount of fuel required to fly for 30 minutes at holding speed at 450 m (1 500 ft) above aerodrome elevation in standard conditions"
The 30 minutes for a turbine airplane have always been considered at holding speed 1500ft above the airfield, while the 45 minutes for reciprocating-engined airplanes have been considered for a long time at cruise level and cruise speed (although this has been changed last year in EASA land).

That's the thought I had 23 years ago when I had to first learn that regulation.
And lately, it occurred to me that a reliable turbine engine with no fuel is as useless as a non reliable piston engine with no fuel.

I was considering that turbine engined aircraft would be flown by more experienced pilots than piston engined ones. However this regulation probably goes back to the days of the big piston engined airliners such as the DC4 and Constellation.

In those dates it was 4 piston or 3 turbine engines for EDTO, perhaps the thinking is a hangover from the past ?

Does a turbine aeroplane have higher certification standards/accuracy for the fuel system/fuel indicating/fuel consumption predictions?

Luc Lion, the answer is there:

It's just an opinion, but I think it relates more to the distance flown within given timeframe.
Piston being generally slower will cover the same distance in longer time.

Superior pilots operate superior aircraft thus turbines require less sinking (about)* time than dirty props. Simples

/s this post has been made in the spirit & knowledge of sarcasm; all rights reserved.





*German Coastguard in YouTube if you don’t get the joke.

My guess is that they wrote the rule back in the good old fuel-suckin', smoke-belchin', dish-rattlin' turbojet days when one was fuel critical as soon as the gear came up. If they needed to carry 15 more minutes in reserve they couldn't make Idlewild to O'Hare nonstop in winter. It must've been a magical time. I could be wrong though.

Single pistons don’t tend to have feathering.

I always assumed that it was because piston aircraft have a much more variable fuel flow than turbines, because of the manual mixture control. Two pilots can set the same power, but have different fuel flows due to leaning technique - whereas a turbine, always running "lean", has the fuel flow directly proportional to power which is inherently more repeatable.

So, a larger fuel requirement for pistons is to allow for the variability.

@Checkboard, that makes sense.
(unlike all the comments stating that piston engines are less reliable, do not feather, etc ; all things that are unimportant in a zero fuel situation)

Just to put another anomaly into the mix in my day helicopters had a thirty minute reserve and the power source was immaterial, piston or turbine. If the "Flight" archives were still available answers to these "why" questions might have answers.