Classic British Flight Sim

One often reads in aviation reference books of an the range of an aircraft:

In that context does 'range' mean endurance or does the number given (miles, nautical miles etc.) mean acft takes off but has run out of available fuel, which be identified as internal fuel or internal fuel plus specified drop tank fuel capacity, and must have landed having flown the equivalent of the distance given? For example, the range might have been given as 2,000nm at a specified cruising speed and height so that when the aircraft has fulfilled those conditions it must have returned to eearth>

Or does 'range' under specified conditions mean 'there and back?' In the above example that could mean the aircraft can only fly 1,000nm out and would then have to return to the starting point.

'Endurance' yet another ambiguous word.

'Radius of action' - I assume that this radius varies with the time on task at a specified range from the starting point. With our 2,000nm acft this could mean a 500nm out with twice the time taken on the outward leg at the same speed followed by the return 500nm return leg. Or perhaps 250nm outward four times the cruising time on task (equivalent to flying 1000nm) before the return leg of 250nm.


Does anyone know the current accepted real world meaning of these terms? If so I should be interested to know both the current meanings and their sources.

Of course all that is modified by 'reserves' of fuel required by Internation Civil Aviation Law but how do the armed services define reserves in a modern war situation? What is regarded as 'Bingo' these days? If you are out to rescue downed aircrew you will probably stretch your time in the air as much as is prudent - perhaps even a little longer than is wise.

Hi Hobby

This is far too technical a question for me to try and answer but I'll give it a quick shot as I'm supposed to be somewhere else

My interpretation of range would be the distance an aircraft can travel at a given speed and load. The higher the load (max payload) the less range.. all due in no small part to the MTOW.

Endurance is somthing not quoted for civil aircraft (not often anyway) and is a different kettle of fish. Military aircraft will takeoff and go on task. They may have to stay on task for a considerable number of hours (cue the mighty hunter) which has a different ontask speed (depending on ops) and may be able to shutdown an engine. MPA for example would be low and slow and depending on where the incident has happened, it will have a 'given' endurance on task taking into consideration it's get there and get back fuel.

So.. endurance would be the amount of time an aircraft can remain airbourne. Range would be how far the aircraft can travel at normal operating levels

ATB

DaveB :tab:

how do the armed services define reserves in a modern war situation? What is regarded as 'Bingo' these days?

As far as I'm aware there's no difference between war and peacetime reserves, you operate to a Minimum Landing Allowance (MLA) which is basically the bit of fuel in the tank you probably can't use and enough to do an instrument approach into a missed approach to land plus a bit because no one trusts fuel gauges. It may be a bit different for fixed wing as in rotary we don't need a diversion so I think they have to have sufficient to carry out a missed approach to land at their diversion airfield instead so it'll vary depending on where that is on a day by day basis.
The command can impose an extra margin above that based on crew experience, met etc.
Operating the Lynx we tend to get close to MLA most flights as otherwise we'd get nothing done, on the plus side our fuel burn is fairly consistent irrespective of what we're doing, whereas I know the Grey Merlin can almost double it depending on what profile it's flying e.g dip vs cruise flight.
To be honest I think terms like Range and Radius of Action are more marketing terms than anything else, at least for miltary aircraft, once you know what your endurance is you can figure the rest out depending on what you want to do, e.g. if your endurance is two hours, you can stay on task for one hour at a radius of action that's half an hour at cruise speed. Or if you want to know how far you can go on a tank of fuel, it's pretty much your endurance at cruise speed.

Hi Hobby -
This article at CalClassic greatly increased my understanding of those terms, and why quoting one without relating it to the others is meaningless. Each one is the result of complex interaction with the others.
http://calclassic.proboards55.com/index ... &thread=57

If you can get hold of the book "The Sky Beyond" by P.G. Taylor, Chapter 14 has a great description of getting nearly 30 hrs flight from a Catalina with a theoretical limit of about 23.

Cheers
MikeW

Many thanks for the informed replies. These will be put to good use in the forthcoming series of Sea Hawks,

I shall have to visit Calclassic tomorrow (Tues). Having an ant-flu injection tomorrow mid day so shall look forward to a cheery afternoon at Calclassic.

If I can just add a word on this : best endurance may be at a speed which does not give the best range ; it will come at the point where the lowest fuel consumption per hour occurs . Greatest range is usually obtained at the minimum drag coefficient speed, which is usually higher than the best endurance speed , and produces the greatest miles per unit of fuel used . Both of these figures are contained in almost all performance charts, and used, because for a diversion best range is needed, whereas for a hold, best endurance is required

Nice topic...

Of course, on military jets, the amount of free gifts hanging on the wings and belly makes some difference. It would be very interesting to see what difference to range a couple of 500 pounders made on a Bucc. - on wings Vs internally carried!

If I can just add a word on this ..

That's pretty much what I was trying to say CS but you said it much better ;-)

What HE said Hobby

ATB

DaveB :tab:

For the past few days I have, at Steve's request, been adding 'gifts etc.' under the wings of the Sea Hawk. Later today I plan to fly from Lossiemouth to Ford to see what differences, if any, such 'addons' make to fuel consumption. I wrote 'if any' because I am a complete tyro at acft cfg modification. This will have to be done several times to examine the differences and to see whether one can produce consistent results for the same loads.

More later - I hope.

For emfrat: An excellent article from Calclassic site. On my setup some eighteen A4 pages long and well worth printing out.

Flight from Ford to Lossiemouth this afternoon at 30,000ft. Total time from parking to parking 94mins. Total flight time, wheels rolling on runway to end of landing run: 83 mins. Cruise speed throttled to maintain as closely as was possible 420kts ground speed with no weather applied - but FS9 appeared to put in a side wind 270*/21kts at 30,000ft. Aircraft loaded to carry just two 88gall (UK Galls) drop tanks.

Current engine somewhat frugal in fuel usage compared to real acft.