Cruising Altitude... technical question.

[Pilot Oatmeal]

Right, my question is, does the cruise speed (i) reveal the cruising altitude that aircraft would fly on a sector in AWS? 

For example, the Dornier 228-100 in AWS says that it cruises at 28,000 feet.  However I know that this turbo prop is not pressurised, so unless you want all the passengers to be rendered unconscious/suffering from hypoxia (and the pilots for that matter) you wouldn't cruise anywhere near that altitude. 

Also, for the smaller planes on small routes where the aircraft may not get to a high altitude, are all these cruising altitudes referred to as Flight Levels (i.e. on the intl standard pressure setting, i.e. 1013.2 or 29.92)?  Or do they use an "average" regional pressure setting (i.e. QNH, altimeter setting)?

If the route altitudes are taken from the cruise speed (i) section then that's an error, the only way that aircraft would get to that altitude would be if all the pax and pilots were given external oxygen.  However I see that 28,000 feet it's "actual" ceiling, just not one that they'd use on a passenger trip. 

[ArcherII]

I'd like to know this as well, because the Navajo's ceiling in AWS is 10,000ft and in reality the earlier -310 model you could fly it at 24,000 (FL240) with supplemental oxygen tanks - 5hrs if 1 pilot zero pax, or 01:30hrs if full pax.


edit reason: missed oxygen from the sentence.

[Sami]

Max cruising altitude is displayed next to aircraft information, on the (i) hover. It is common for the whole fleet group (as well as other performance data, excluding fuel usage).

The actual cruising altitude is determined separately for each sector (not displayed to users). The flight profile is hence dependant for example on the flight distance. In other words on a long route the jet can climb all the way to the ceiling (step climb on long routes is taken into account in fuel consumption) while on very short hops it has to stay at a lower level. The system determines the max cruising altitude for each route by looking at the plane's climb/descent rates, speed, distance and calculating it so that it will go to max possible level to attain a cruise flight there for at least some 20-30 nm.

And the actual TAS at cruise level is of course calculated correctly depending on the altitude too. All-in-all the flight time and performance calculations are very close to what happens in reality. (taxi times will differ a bit as it's based on the airport size class, 1-5)


(QNH differences are meaningless to these calculations)

[Pilot Oatmeal]

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The actual cruising altitude is determined separately for each sector (not displayed to users). The flight profile is hence dependant for example on the flight distance. In other words on a long route the jet can climb all the way to the ceiling (step climb on long routes is taken into account in fuel consumption) while on very short hops it has to stay at a lower level. The system determines the max cruising altitude for each route by looking at the plane's climb/descent rates, speed, distance and calculating it so that it will go to max possible level to attain a cruise flight there for at least some 20-30 nm.

So your saying that the Dornier 228 would fly at 28,000 Feet on a 620 NM range trip (the a/c's maximum range).  Because that is an error.

(QNH differences are meaningless to these calculations)

How is it? If like you and I said the aircraft is on a very short trip and the aircraft is unpressurised they may fly below the transition layer (I know it's different country to country), in the UK for example it's 3000 Feet, I believe it's like that for most of Europe.  SO for example, flying a piper navajo on a 60NM trip might not go above the transition layer , it's highly possible because I've done it many times in my life.  

[Sami]

So your saying that the Dornier 228 would fly at 28,000 Feet on a 620 NM range trip (the a/c's maximum range).  Because that is an error.

If Do-228 is unpressurized and it's fleet settings have a cruising altitude >FL100, then it's a data error.

How is it? If like you and I said the aircraft is on a very short trip and the aircraft is unpressurised they may fly below the transition layer (I know it's different country to country), in the UK for example it's 3000 Feet, I believe it's like that for most of Europe.  SO for example, flying a piper navajo on a 60NM trip might not go above the transition layer , it's highly possible because I've done it many times in my life.  

It makes no difference whatsoever to cruising speed & flight time on the route if you are flying on local QNH or 1013 (the 'true' altitude differs only a a few hundred feet maximum in any case)...


(And 'standard' transition ALTITUDE in Europe is by the way 5000 ft - but depends on country/airport. And I think most of UK airports do use 5000 ft, or 6000 ft (London region has 6k); but this is irrelevant)

[Pilot Oatmeal]

If Do-228 is unpressurized and it's fleet settings have a cruising altitude >FL100, then it's a data error.

Ahh okay, should that be in bugs then?

It makes no difference whatsoever to cruising speed & flight time on the route if you are flying on local QNH or 1013 (the 'true' altitude differs only a a few hundred feet maximum in any case)...


(And 'standard' transition ALTITUDE in Europe is by the way 5000 ft - but depends on country/airport. And I think most of UK airports do use 5000 ft or 6000 ft (London region); but this is irrelevant)

Yes I understand that, I was just wanting to see how the system was working it out.

The standard transition layer outside of the London area in the UK, is 3000 feet, like you say around the London area it's 5000 ft or 6000ft. 

[Sami]

Ahh okay, should that be in bugs then?

No need, checked just and corrected to master db.