I thought of it with a related sort-of- question, more of an amazement at looking at one above a police scene…
Damn those things are stationary, like it’s parked. Are there design specs for “allowable–goal design” circles of error in holding still?
Imagine query 1) as an Olympic event requiring allowable give–which, come to think of it, must be a well known and analyzed aerodynamic engineering topic from forever.
Have they ever prototyped copters with copter-to-copter (or even ground-to-air) inflight refueling? I doubt it, thinking about military tactics and operations, but it would be grand for establish Olympic events as in query 1). But one Israeli firm, I know, has developed electrical leads for stationary-but-relocatable quadcopter for surveillance, so there’s that.
Helicopters can be refueled from [Aerial refueling - Wikipedia](the ground, from a ship, or from a tanker plane in flight). Copter-to-copter I doubt exists; there doesn’t seem to be a need for such a thing.
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I don’t know about in-flight refueling, but I have a somewhat related experience, when learning to fly a Bell 206 that has a semi-rigid rotor, i.e. the blades can “flap” vertically.
We took off in marginal conditions, and eventually set down in a wind that was now gusting to 60 knots. Provided the rotors keep turning at full speed, the plane of rotation of the blades is controlled adequately in almost any conditions by cyclic (variable angle of attack throughout rotation). But as the rotation slows, aerodynamic forces decrease and cyclic control is gradually lost. In a moderate wind, it’s not a problem if the blades then flap up and down a little, because there’s obviously a reasonable amount of clearance. But in such a strong wind, there’s a risk that the blades may flap so much that they strike the tail boom. We had to sit there on the ground for several hours, hand on cyclic with blades turning at full speed, including one refueling from a truck, until the wind dropped sufficiently that we could safely allow the blades to slow down. Fortunately my instructor was ex-RAF, so I got several hours of war stories while we sat there.
I don’t know specifically, but I’ve heard of long term hovering tests to measure the efficiency of blade designs based on long term fuel consumption. All I can recall are tests of maybe 8-10 hours of hovering.
Seems like if you hover low enough, someone could just run a refueling hose up to the helicopter and refuel you, either from a truck or a stationary tank.
At that point, the pilot’s endurance or mechanical failure would be what puts a stop to the experiment.
dual controls
Inside hanger
fuel line & lubricant line attached
ramp to get to level possible to step inside
several pilots to work in rotation
remain airborne until something breaks
Auto pilot with hover capabilities and only problem is when something finally breaks.
Do without pilots
set record
waste $$$$$$$$$$
I like it, someone with $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ do it for giggles.
I can see you as a Captain of Industry talking/barking at your assistant: bam-bam-bam getitdone.
(BTW, are you a Captain of Industry?)
BTW, are helicopter Pilots-in-Command referred to as “Captain?” There’s a thread on that somewhere regarding fixed-wing civilian and military titles; I don’t think copters came up. (As it were.)
ETA: where the hell has LSLGuy gone to?
When I was flying Hueys in the Army(80-85) the pilot in command was just called pilot in command not captian, Of course since I was a captain I was also called captain at other times:p
The longest endurance helicopter flight of all time is 18 hours 41 minutes at the Yuma Proving Ground in Arizona but I don’t think there is any reason that it couldn’t be longer if you really wanted to.
One of the strangest records of all time is the longest endurance records in an airplane. It wasn’t a military plane or even an airliner. Nope, it was done as a publicity stunt in a lowly Cessna 172 in 1958 - 1959 (yes, it really spanned calendar years). The non-stop time was 64 DAYS 22 hours. The two pilots literally lived in it in the air the whole time and hauled up fuel and supplies from a chase car in the Las Vegas area.
If they could make something like that work in a moving airplane, it should be much easier in a hovering helicopter.
Prior to just a few years ago hovering was 100% manual. How still they stayed was a matter of pilot skill versus how gusty / turbulent the air is at that place & time.
Certainly one of the design goals of any helo is/was control response that makes hovering possible with less than superhuman skill. The controls need to be sensitive enough but not twitchy; enough stability but not too much. Given that almost every takeoff and landing includes a bit of hover, there’s not much special emphasis needed for mid-altitude hover.
One of the challenges for manually hovering at a few hundred feet is you can only perceive your motion against the ground background with X angular accuracy. So a pilot who can hover +/- 1 foot at 50 feet of altitude would perhaps be able to hover not much better than +/- 10 feet at 500 feet. It’s not quite that simple, but that gives a feel for the issues. How stationary a helo really is can also be hard for you on the ground to determine accurately just by looking up at it against a featureless sky. It may be moving a lot more than you think.
Nowadays high sensitivity IRS coupled to GPS with computerized autopilots can hold station within a foot or so in reasonable winds even at considerable altitude. There can also now be GPS-driven instrument guidance for manual hovering. So rather than looking out the window to see and correct his motion against the ground the pilot can drive to a spot that looks promising out the window then tell the computer: show me an instrument to help me stay right here. Then he just follows the displayed guidance as best he can.
In the commercial helicopter industry, just as in the airlines, Captain and First Officer titles are used to denote those pilots who are qualified to be Pilot In Command, and those who aren’t (yet).
I spent 11 years maintaining and crewing CH-53Es in the Marines. Good times… mostly. Only feared for my safety a couple times during HAAR (helicopter air-to-air refueling). Definitely let you know which pilots were truly gifted “sticks”.
enipla’s second link is what is known in the Marine Corps as a FARP - Forward Arming and Refueling Point. There are internal fuel tanks and a pallet with pumps, hoses, valves, etc. that can be loaded into the cabin of a CH-53E, and flown to a FARP site to fuel ground vehicles or other helicopters (usually Hueys/Cobras). For arming, another -53 or an MV-22 will have ammo and a load crew aboard to rearm the vehicles/helicopters.
HIFR - Hover In-Flight Refueling. It’s a longer evolution than refueling on the ground or flight deck, since the hovering helicopter is burning a not-insignificant amount of the fuel that’s being pumped aboard, and the HIFR hose & fittings are smaller in diameter (hence, a lower flow rate) than the standard SPR hose & fittings.
Much longer than that, in fact. Nearly 31 hours and nine HAARs, New York-Paris nonstop in 1967, to commemorate the 40th anniversary of Lindbergh’s Atlantic crossing. 8MB .pdf link
Rigid rotor systems and fully-articulated rotor systems also ‘flap’. With a semi-rigid system such as used on the Bell 206 JetRanger or the Robinson R22 and R44, the blades flap as a unit about the teeter hinge. In a helicopter like the Hughes/Schweizer/Sikorsky 300 (aka TH-55), there is a fully-articulated rotor system because there are more than two blades. A fully-articulated rotor system has ‘flapping hinges’ to allow the blades to flap, and lead-lag hinges to allow for the Coriolis effect when the blades flap. Rigid rotor systems only have the feathering hinges (the other systems also have them), and the flapping and feathering are handled by the flexibility of the rotor blades.
Of course, the helicopters I flew (R22s and Schweizer 300CBs) are not sophisticated enough to have automated systems. They did have a throttle correlator (governor) though.
When I was training, the ground school video (or maybe it was an instructor) said that there used to be a requirement in the practical test, for the applicant to demonstrate the ability to hover within a circle of a defined diameter. That requirement was later dropped, because you have to do it anyway on landing.
