denopa wrote:
spending 20 minutes at 160kias 14.5usg/h is a nice way to extend the range
Did you do calculations on that? For my aircraft staying in cruise longer and descending at 2500 fpm gives 25 miles more range vs descending earlier at 1500.
I’d struggle to maintain pressurisation at any lower power settings, so to get down faster means using airbrakes and/or lowering the gear while still using 14.5usg. So I don’t really have a choice :-)
I’d struggle to maintain pressurisation at any lower power settings, so to get down faster means using airbrakes and/or lowering the gear while still using 14.5usg. So I don’t really have a choice :-)
A bit off topic but our Mirage never had problems maintaining cabin pressure at any reasonable descent power setting. So it might be worth to check the cabin seals.
Even below 22"?
Even below 22"?
It has been a while but I actually did own two different 1992 Mirage and I remember both would maintain max cabin differential at 20". We once did a one hour holding at FL170 using absolute minimum power setting required to just keep the plane in the air and the cabin did not complain.
The only time we lost cabin differential was when performing stalls at FL150 with the engine close to idle.
I may indeed have a leak somewhere then. The door seal most likely… Thanks.
Did you do calculations on that? For my aircraft staying in cruise longer and descending at 2500 fpm gives 25 miles more range vs descending earlier at 1500.
For sure there’s difference between turbine TBM and piston Extra 400 (as I understand the fuel burn was reffered to it, regardless thread is about Extra 500).
I’m sure there is a difference, but what puzzled me was @denopa saying “big fan of long slow descents (…) is a nice way to extend the range”. I thought staying high extends range regardless of engine type. If I’m wrong, I’d be happy to hear about it.
loco wrote:
I thought staying high extends range regardless of engine type. If I’m wrong, I’d be happy to hear about it.
I think the difference is more dramatic with turbines, thus makes it more efficient to stay higher longer.
Flyingfish wrote:
The E500 has a lower Vne – not sure if it is the consequence of higher mass or longer tail – I’d guess it’s the tail.
I hear the certification requirements are different on pistons and on turboprops; the latter use Vmo where pistons use Vne, and the requirement on it are more strict, leading to lower values for the same airframe.
Obviously I know nuffink about TPs and jets, but the difference must be in the fuel flow per mile travelled being 2x to 3x lower at say FL300 than at say 2000ft. A 747 would possibly not make it across the Atlantic if flying at 2000ft… So it pays to stay high as long as possible. Loco obviously knows about this, along with other TP owners here e.g. @quatrelle @eal (and others) whereas pistons, especially non-turbo ones, have a fairly constant fuel flow per mile versus altitude once above about 40% of their ceiling (and then it actually gets worse in the last few k feet within the operating ceiling e.g. above FL170 for a TB20) and then the objective in a descent is to not get too fast because flying fast means more drag so is inefficient, and together with the desire to not get too low too soon, the best way to “make some avgas back” is a long slow continuous descent. OTOH, and I am not sure if we have jet pilots posting significantly here, but big jets do continuous descents, so presumably they have other reasons; I think they cut the power and actually glide all the way down at Vbg if they can.
