Short Cruise Alt Tip

[nzav8tor]

Hi everyone,

New to the forum and browsing some of the past topics and thought I'd include a small tip for selecting a cruise flight level for trip distances of less than 200nm.
Based on jet aircraft performance but suitable for high powered turboprops such as B1900.
Basically, take the distance rounded to the nearest whole number, drop the last digit and add 5 and theres a good cruise altitude.

For example...

Trip distance, 174 nm

Make it 170, drop the 0 and add 5 make a cruise level of FL220

Then of course adjust it for compliance with route level limitations, in NZ, north bound odd, south bound even.

Hope this is of some use as New Zealand has alot of quite short legs flown by high performance jets.

Regards,

Dave

[ZK-Brock]

Dave, thanks bruv! I'll bear this in mind...BTW, welcome to the forums Introduce yourself on the appropriate thread on this board if you'd like

[ardypilot]

Thanks for the tip, does this rule apply in real life flying too?

[Charl]

Hi Dave, welcome and thanks!
Where did that come from, is it based on fuel economy?
There's obviously a lower limit for this, and an altitude limit other side.
{Gets out circular slide rule, aviator edition.}
174nm trip
climb out 200kts 1800 fpm...12min to FL22
cruise 250kts 16 min
Letdown (FLx3nm) 66nm @250kts 16 min
Total trip 44 minutes.
OK
What about up and down no level cruise?
Up: 5min to 9,000ft
Down: 6min
Total trip 11 minutes.
44 nm covered.
No jet would do such a short trip, this is what Cessna 172's were made for.
Wonder where's the cutoff?
(I also have a number fetish, sorry)

[nzav8tor]

Haha, well whatever floats your boat Charl...!

Its a real world tip we use for short flight planning in the cockpit.
Flight computer? You know we don't actually use those in real life! (Like algebra oh but your a number freak right!)

Sure, over 200 nm the cruise is long enough that you have enough time to make it to a higher altitude and benefit from the reduced fuel consumption.
On a trip around 50 nm it will still work for FL100 but generally things are happening so damn quick you just follow ATC instructions and one procedure is leading into another, SID to STAR or straight into a transition or vectors for the approach.

Scheduled airlines obviously won't do trips this short in jets but it is quite common for turboprops and biz jets.

Dave

[Charl]

Well I suppose if I can get in a car and drive 2km to the dairy, then 50nm in a bizjet doesn't sound so bizarre.
Except that for a 50nm trip, in theory an hour's drive point to point, I think I'd take on a Lear, even if it were in a hurry.
Especially if driving through Auckland to the airport were part of the latter equation!

[nzav8tor]

Sometimes we have a short ferry leg to pick up pax or coming home after dropping them off, Budapest to Vienna and local flights within austria are very short and busy.
These are alot of fun as you are normally very light and have no pax to worry about.
We also do medical flights with organs for transplant around europe, best pax, they don't complain and are normally light on baggage.
Hearts, lungs, livers the odd pancreas too.
Had a flight from Salzburg to Innsbruck recently and was able to do a 45deg turn after takeoff to make a tight departure procedure as we were time limited with our heart on ice... Not much compared to proper aeros but its fun in a jet... Climb rate over 5000 fpm...
Wheels off to wheels on was about 23 mins, TOC (FL120) in about 2 1/2 mins. ATC can't keep up with you normally!