Fuel Decision in Military Aviation
Whilst managing fuel loads is obviously a prudent measure it has to also take account of the task in hand. I can recall at least one occasion when I was working in MOD when Ascot Ops contacted me to advise that the planned load couldn't go as it would mean staging Gander. Having spent some time justifying to a civil servant, who was heavily focused on costs, that it was essential that the load was moved, I politely informed Ascot Ops that the only reason that the flight was happening was to carry the load and if this meant staging Gander so be it.
Alternate fields
One cool morning (while doing my military service) I overslept and I did not turn on the TACAN on the base I was stationed. The duty ATC gave me a bollocking and asked me what the military aircraft coming to land would do while the TACAN was off. I did not answer (about the alternate) and he appreciated.
So do FJ always include an alternate airport when they file a flight plan?
One cool morning (while doing my military service) I overslept and I did not turn on the TACAN on the base I was stationed. The duty ATC gave me a bollocking and asked me what the military aircraft coming to land would do while the TACAN was off. I did not answer (about the alternate) and he appreciated.
So do FJ always include an alternate airport when they file a flight plan?
I don't own this space under my name. I should have leased it while I still could
Ri S, indeed they do. You have an emergency diversion in range of your destination and carry sufficient fuel for a procedural recovery at destination and diversion to the alternate.
Depending on distance to the alternative that spare fuel can be quite significant. In the event there is no suitable diversion there is a procedure called Island Holding but that is not valid for all aircraft and is usually only relevant for transient weather events such as local thunderstorms.
Depending on distance to the alternative that spare fuel can be quite significant. In the event there is no suitable diversion there is a procedure called Island Holding but that is not valid for all aircraft and is usually only relevant for transient weather events such as local thunderstorms.
PN,
Not quite correct. For fast jets, you must touch down at destination with sufficient fuel to get to the alternate, fly an approach appropriate to the weather and then touch down at the alternate with a specified minimum fuel quantity (determined by unusable fuel, gauging accuracy, c.g. limits etc and probably one visual circuit). If the weather at the diversion is colour state 'white' or better (1500 ft cloudbase, 5000 m vis) then an 'appropriate approach' will be a visual join, and if 'green' will invariably be an instrument approach. The approach requirements at destination will also be weather and approach aid dependent but if radar vectoring to an instrument approach is available then you would not plan to recover for a procedural approach.
Not quite correct. For fast jets, you must touch down at destination with sufficient fuel to get to the alternate, fly an approach appropriate to the weather and then touch down at the alternate with a specified minimum fuel quantity (determined by unusable fuel, gauging accuracy, c.g. limits etc and probably one visual circuit). If the weather at the diversion is colour state 'white' or better (1500 ft cloudbase, 5000 m vis) then an 'appropriate approach' will be a visual join, and if 'green' will invariably be an instrument approach. The approach requirements at destination will also be weather and approach aid dependent but if radar vectoring to an instrument approach is available then you would not plan to recover for a procedural approach.
I don't own this space under my name. I should have leased it while I still could
LOMCEVAK l, I was trying to keep it simple and generic. For procedure o embraced any variation on procedures and not specifically a procedural approach.
Last edited by Pontius Navigator; 10th Apr 2016 at 11:53. Reason: Don't you just love auto correct
I don't own this space under my name. I should have leased it while I still could
Both I guess but I think you will find Civair has similar rules though as you can never be sure a runway will remain open. Queue BEagle.
Where en route diversions are concerned, they may be planned and closely monitored but nit usually pre booked.
Where en route diversions are concerned, they may be planned and closely monitored but nit usually pre booked.
On cue then, for a typical AT/AAR aeroplane:
'Final reserve' is the minimum fuel required to fly for 30 minutes at 1500ft above the alternate aerodrome.
'Alternate fuel' is the fuel required from the missed approach point at the destination aerodrome until landing at the alternate aerodrome. It takes into account the fuel required for the missed approach at the destination aerodrome, climb to enroute altitude, cruise and descent and approach at the alternate aerodrome.
'Minimum Diversion fuel' is the sum of final reserve and alternate fuel.
But then you have to take into account taxi fuel, 'trip fuel' (which is the actual fuel calculated to be used from take-off to landing at destination), contingency fuel (typically 5% of trip fuel needed from an enroute waypoint, or ideally from take-off), and for a tanker, any 'offload fuel' for receivers.
This will give you 'minimum brake release fuel', which is the sum of trip fuel, contingency fuel, offload fuel and minimum diversion fuel.
'Block fuel' is what's in the tanks prior to start. Subtract taxi fuel and the 'extra fuel' is what's left once 'minimum brake release fuel' has been subtracted.
Of course the airlines have various other rules which enable them to cut their reserves to the bone. But one major point is that the level at which an aeroplane flies from destination to alternate cannot be assured, nor can the route. So even normal legal airline planning can be caught out by ATC issues, as Ryanair found out when several of their aeroplanes had to divert on summer in Spain, following bad weather at destination. They'd all loaded a prudent extra margin of fuel, but when the air traffickers held them at much lower levels then anticipated, the crews found themselves getting rather tight on fuel. Which was emphatically NOT the fault of the airline or its crews, but was entirely due to the incompetence of Spanish ATC. The reason it hit the headlines was that they had the largest number of flights forced to divert.
Modern planning techniques should include the ability to specify the level and met conditions for the enroute phase of a diversion, as well as the desired landing fuel at the alternate (normally assumed to be the unusable fuel in tanks after final reserve has been used). This means automating the calculations provided in the Flight Crew Operating Manual, something of which traditional computer flight planning systems are not usually capable.
For example, normal planning for a 315 nm diversion assuming met conditions of the day and a climb to optimum altitude might result in a theoretical minimum diversion figure of 5945 kg. But factor in an adverse wind and a diversion held down at, say, 10000 ft and ISA +5 and this rises to 6445 kg. Which might mean arriving at the alternate with a fuel state below legal final reserve unless this had been taken into account.
For AT/AAR, accurate fuel planning is essential if the multi-role capability is to be used for a particular mission. A wet-finger guess or 'fill it up please' could well prejudice the payload available - that unnecessary extra 2 tonnes of fuel could well have been useful payload!
'Final reserve' is the minimum fuel required to fly for 30 minutes at 1500ft above the alternate aerodrome.
'Alternate fuel' is the fuel required from the missed approach point at the destination aerodrome until landing at the alternate aerodrome. It takes into account the fuel required for the missed approach at the destination aerodrome, climb to enroute altitude, cruise and descent and approach at the alternate aerodrome.
'Minimum Diversion fuel' is the sum of final reserve and alternate fuel.
But then you have to take into account taxi fuel, 'trip fuel' (which is the actual fuel calculated to be used from take-off to landing at destination), contingency fuel (typically 5% of trip fuel needed from an enroute waypoint, or ideally from take-off), and for a tanker, any 'offload fuel' for receivers.
This will give you 'minimum brake release fuel', which is the sum of trip fuel, contingency fuel, offload fuel and minimum diversion fuel.
'Block fuel' is what's in the tanks prior to start. Subtract taxi fuel and the 'extra fuel' is what's left once 'minimum brake release fuel' has been subtracted.
Of course the airlines have various other rules which enable them to cut their reserves to the bone. But one major point is that the level at which an aeroplane flies from destination to alternate cannot be assured, nor can the route. So even normal legal airline planning can be caught out by ATC issues, as Ryanair found out when several of their aeroplanes had to divert on summer in Spain, following bad weather at destination. They'd all loaded a prudent extra margin of fuel, but when the air traffickers held them at much lower levels then anticipated, the crews found themselves getting rather tight on fuel. Which was emphatically NOT the fault of the airline or its crews, but was entirely due to the incompetence of Spanish ATC. The reason it hit the headlines was that they had the largest number of flights forced to divert.
Modern planning techniques should include the ability to specify the level and met conditions for the enroute phase of a diversion, as well as the desired landing fuel at the alternate (normally assumed to be the unusable fuel in tanks after final reserve has been used). This means automating the calculations provided in the Flight Crew Operating Manual, something of which traditional computer flight planning systems are not usually capable.
For example, normal planning for a 315 nm diversion assuming met conditions of the day and a climb to optimum altitude might result in a theoretical minimum diversion figure of 5945 kg. But factor in an adverse wind and a diversion held down at, say, 10000 ft and ISA +5 and this rises to 6445 kg. Which might mean arriving at the alternate with a fuel state below legal final reserve unless this had been taken into account.
For AT/AAR, accurate fuel planning is essential if the multi-role capability is to be used for a particular mission. A wet-finger guess or 'fill it up please' could well prejudice the payload available - that unnecessary extra 2 tonnes of fuel could well have been useful payload!
Last edited by BEagle; 11th Apr 2016 at 07:24.
I don't own this space under my name. I should have leased it while I still could
BEagle reminds me that our Nimrod crib sheets had distance, track, height to fly and fuel required. I think there was also a headwind component factored in but it was prudent to factor in any stronger winds as usually caused diversions at Kinloss. Most diversions on Scotland were simply to TOC/TOD with no level cruise. If you were canny you might select a lower transit to benefit from a lower headwind and save on climb fuel.
We, that is some pilots, don't always follow the rules. We did a flight to Kef in the Shack. Conditions were bad at both ends and our diversion was our departure airfield. We had sufficient fuel for an instrument approach, overshoot, visual circuit and land or divert.
After the initial approach we glimpsed the airfield and the captain elected for a second instrument approach which put us below minimums. We got in. Had we had to abort I guess we might have managed Benbecular or Stornoway but he would have had some explaining to do.
We, that is some pilots, don't always follow the rules. We did a flight to Kef in the Shack. Conditions were bad at both ends and our diversion was our departure airfield. We had sufficient fuel for an instrument approach, overshoot, visual circuit and land or divert.
After the initial approach we glimpsed the airfield and the captain elected for a second instrument approach which put us below minimums. We got in. Had we had to abort I guess we might have managed Benbecular or Stornoway but he would have had some explaining to do.
Beagle - driving West on the M4 yesterday we could see the procession of aircraft descending into Heathrow on the less common approach from the West. Mrs TTN (bless her) said "what if it's raining or foggy and they cant see the runway?" Cue long discourse on runway approach aids, which then led onto the question of alternate airfields, diversion fuel etc.
I must sit her down to read your post #69 !
I must sit her down to read your post #69 !
TTN - I am jealous - any mention of anything aviation-related and Mrs W's eyes glaze over and I get another 3 pages of pseudo-psychology read to me from some American self-help book, and my eyes glaze over!
TTN,
Yesterday lunchtime by any chance? If so, you probably saw a beautifully hand flown approach in one of our flag carriers finest 777s....
Yesterday lunchtime by any chance? If so, you probably saw a beautifully hand flown approach in one of our flag carriers finest 777s....
Since Virgin Atlatnic have been the UK's flag carrier ever since some other british airline removed the union flag from their aircraft in 1997, this must have been a rare sighting indeed as surely it's only Virgin Australia which operates the company's Boeing 777-300s?
Was about that time, megaton. I was asking Mrs TTN to identify the aircraft but her skill in that field is even worse than mine. I am restricted to "a big one with two/four engines" and I saw quite a few of the former, which could well have been the 777 you referred to !
Particularly testing conditions too IIRC
I don't own this space under my name. I should have leased it while I still could
TTN, quite right, there are friendly military, enemy military, Chinooks, helicopters and civilian, 2 jet, 4 jet, prop and finally puddle jumpers.
