Cruise power - fuel for 3 hours minimum

[Head Turner]

I believe that fuel tanks fitted as standard should hold enough fuel for a minimum of 3 hours at cruise power in Standard Conditions ( sea level + 15 deg etc)

Anything less and more time is spent refuelling and paying costly landing fees than flying.

So what do you think should be a standard and why?

[Shawn Coyle]

Most light helicopters probably don't spend a lot of time cruising - in fact, if you spend that much time cruising, you could probably do it more cheaply in a fixed wing.
While having a large size fuel tank is not a bad idea, what is more important, and missing on nearly all light helicopters, is an easy way to defuel them to get the weight down if you need it as payload.

[Head Turner]

Defuelling is a problem for sure but my point is that there are several twins that hardly do 2 hours 20 minutes and when you have either one longish trip or several shorter hops finding fuel within a tight schedule is a headache.

[NickLappos]

Three thoughts:

1) Why not think of the range provided by the fuel? Fuel is usually used to go somewhere, the fuel amount is usually resolved as a range, not a time. 3 hours at 60 knots might be the same as 2 hours at 90 knots.

2) Fuel tanks weigh about .5 to 1.0 lbs per gallon, so each additional gallon of gas allows less payload, even if the tank is not full.

3) Human endurance - I am good for about 2.5 before I need to land, sorry!

[Gomer Pylot]

I prefer more fuel capacity, mostly because I like to keep some reserve. If the tanks only holde 2.5 hours of fuel, that means you can only fly 2 hours max, and that's stretching it under many conditions. Nick's point about cruise speed is valid - 2 hours at 100 kts means a lot less range than 2 hours at 150 kts. That's why current Bell models are so limited - they don't carry much fuel, they are slow, and PT6s suck the fuel at a horrendous rate, so the range is pitiful. The BO105 is another model with range problems. The current 206 models, with ever larger engines, don't do well, either. If you're doing many short trips, then the speed becomes much less important.

[CyclicRick]

All our 206's have range extenders fitted which gives you about 3:15 with a little reserve. Our 205's get about 1:50 with standard tanks but with the 44gal aux tanks fitted it's about 2:20 which is far more useful a range ( plus you can still use them as seats!).
I managed 3:30 in our AS350 up at 9000ft doing 60-80 kts on border patrol in Macedonia (good job the seats were comfy, I wouldn't like to do that in a 206 :uhoh: )

[pa42]

Pity the poor manufacturer and all his starving employees. The perfectly good helicopter is flying well and selling well, when managment 'listens' to the calls for increased range. "Sure, we'll increase tankage by 1/3!"

Out comes the new model. The Press gets to fly it & 'critique' the performance. What's this? The new model is SLOW, and has very limited altitude capability, and almost no cargo capacity! "What a dog," the press cries.

Bingo, another bankrupt helicopter manufacturer! All because The Press chose to fly it with full fuel, as, "of course," all the operators would do. Or so they believe.

Ergo, I don't see a lot of market for bigger tanks. The ferry pilots, of course, a)have no voice in the matter, and b)are frequently time-builders, anyway. So the manufacturers have little to gain by increasing tankage, and a great deal to lose!

[One brilliant application for the R22 optional (?) aux tank: Showcopters has replumbed theirs to carry the airshow smoke-generator-oil. 'We don't need no stinkin' avgas!']

Sorry to be so negative, Heady, but you may need to develop an STC for bigger tanks all by yourself. Or you could emigrate to the USA, where landing fees are a rarity and the 'trackless wilderness' is absolutely LITTERED with MoGas outlets. All tended by lonely farmer's daughters.

Dave

[NickLappos]

pa42,

Boy you hit the nail on the head. I can't tell you how many times I have had to try and talk people out of filling up the tanks and reducing payload. Often a "study" of two aircraft starts off with full tanks, even though one aircraft has 100 nm more range in that condition. Or the "study" has both aircraft carry 2 hours of fuel, even though one goes 60 nm farther in that 2 hours.

I must say, we build aircraft to sell, so if the market wants longer range, more tankage or the rotor on the bottom, we will do it.

[delta3]

I could not use a heli it would not fly 3hrs
That does not mean it should be standard
My R44 most of the time is planned for 2:30 up to 2:45 because i use it door to door long distance (4:30 total at 105 kts) at least 4 times per month
A plane does not beat that because it is not door to door (I cant afford a Gulfstream, but I might be thinking of a TT62)
CyclicRick : my Robby is fine, even the wife and dog don't mind (they hate cars)
Head Turner : defuelling a robby is very simple, it just takes a hose and some jerrycans..

a privateer

[200psi]

PA 42 & Nick

Horses for courses try making that argument to the guys involved in offshore SAR.

[Bertie Thruster]

My HEMS unit average flight time this year is 12 minutes. (320 hrs, 1600 landings, 1200 starts,) 2 hr endurance is plenty!

[Head Turner]

To you all who have replied:-

Sorry, I thought that I was being specific in my opening topic stating that the basic fuel load should give 3 Hours at CRUISE POWER at SEA LEVEL in ISA Conditions.

OK we don't always need that amount of fuel but we very often need that CAPACITY to carry that amount of fuel when longer flights are required.

For some of you I read into what you are saying and get the impression that you fill to capacity and then decide how many passengers or freight you can then carry.
Surely you should do your CG calculations based on the task and then add the maximum fuel allowing for weight and performance.

I appreciate that B206's have range exrenders and they need them to go any sensible distance.

Remember you designers that not all helicopters are flown in areas where there are abundant refuelling places. Get real and look to the tasks and not the shiny plush FBO's that you seem to habitate. For me helicopters are work tools to do a wonderful job of Door to Door and not airfield to airfield that's for planks.

So please helicopter designers of the future please put in tanks with capacity the pilot in command then has the choice of how much to put in dependant on the variety of factors that a particular task presents.

[GLSNightPilot]

Down here in the GOM we seldom top off, and it's a luxury when we can. At night, I often am empty or close to it, so I can often top off, and always do if I can. I ain't gonna head out over the water short on fuel, no way, nohow. I agree with you Head, that the capacity should be there if possible. If I have to fly a 412, then I'm always short on fuel, because it's so slow, and burns fuel so rapidly. The S76 actually holds less fuel, but it goes much faster and burns less, so the cruise time is much higher. The S76A++ holds 3 hours nominally, but you can get more if you go high, because the burn is less and you have to reduce power to stay below Vne. The 412, OTOH, has about 2.5 hr fuel, and you have to really watch that. But that half hour of fuel difference translates to about 140NM difference in range. It's not really as much about the endurance in time, but about how far you can go on the fuel you have.

[diethelm]

My personal bladder typically fills before the aircraft bladder empties so three hours is plenty. As I get older, I have a feeling that this ratio inversion shall continue to diminish the time available on task.