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More work needed to clear A400M for helicopter refueling

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posted on Nov, 3 2015 @ 02:29 AM
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A problem has been found during testing to certify the A400M as a tanker able to refuel helicopters. Pilots of the helicopters have been able to get into the precontact position but when they try to move ahead to contact the wake turbulence makes it almost impossible to connect to the drogue.

Airbus has stated that I'm its current configuration it will be impossible to refuel helicopters. They were able to prove the tanker concept with fixed wing aircraft, but helicopters won't be in a position to see the tailplane, and the wake makes it impossible for them to connect to the 90 foot drogues that are in use today. Airbus has started a study to develop 120-150 foot hoses to see if they are possible to stabilize and move the helicopter back away from the wake.

They've also found that if paratroopers jump from both rear doors the wake will pull them around behind the back of the aircraft to a possible collision.

aviationweek.com...




posted on Nov, 3 2015 @ 08:09 AM
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a reply to: Zaphod58

Sounds like they need to go back to the wind tunnel to do some aerodynamic testing and see if a baffle or spoiler can be added to change the shape of the wake turbulence.



posted on Nov, 3 2015 @ 09:26 AM
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a reply to: Zaphod58

You'd think all of this analysis would have been done with computer simulations before the first rivet. Hell of a time to find out.



posted on Nov, 3 2015 @ 09:30 AM
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a reply to: HighDesertPatriot

The initial design didn't call for it to be able to refuel helicopters. That came along later at the request of several customers.



posted on Nov, 3 2015 @ 10:13 AM
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originally posted by: Zaphod58
a reply to: HighDesertPatriot

The initial design didn't call for it to be able to refuel helicopters. That came along later at the request of several customers.


That makes more sense. Why did they use turboprops instead of jet engines? Isn't that kinda going backward?



posted on Nov, 3 2015 @ 10:20 AM
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a reply to: HighDesertPatriot

Turboprop engines handle unpaved strips and rough runways that jet engines don't.



posted on Nov, 3 2015 @ 10:35 AM
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originally posted by: Zaphod58
a reply to: HighDesertPatriot

Turboprop engines handle unpaved strips and rough runways that jet engines don't.


That much I know... so the C-17 was not designed for unimproved runways? Pretty sure I have seen videos of it landing in those conditions.



posted on Nov, 3 2015 @ 10:41 AM
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a reply to: HighDesertPatriot

The C-17 can do unimproved runways to an extend but it can't handle the rough stuff like a C-130 or an A400 can. It is also quite a bit bigger and can keep the Hi-bypass engines farther off the ground than a smaller transport.



posted on Nov, 3 2015 @ 11:13 AM
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a reply to: HighDesertPatriot

Sammamishman is right. The C-17 can operate off some unimproved strips, but the C-130 and A400M can operate on more and worse strips than it can. They flew a C-17 in to a dirt strip fairly early in its career and blew most of the main landing gear tires. They had to fly a C-130 in with replacement tires and jacks.



posted on Nov, 3 2015 @ 12:54 PM
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a reply to: Zaphod58



posted on Nov, 3 2015 @ 01:00 PM
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a reply to: HighDesertPatriot

Like we said, they can land on rough runways, but the C-130 can land on smaller and rougher strips.

In addition to the C-130 having access to rougher strips, a C-17 requires 3,500 feet to operate, if it's extremely light. The C-130 only needs 3,000 feet with a medium load. That's with a 500 foot safety margin added. The J model can takeoff with a heavy load in similar conditions. Props have more constant thrust than jet engines so they actually produce more power at low speed.
edit on 11/3/2015 by Zaphod58 because: (no reason given)



posted on Nov, 3 2015 @ 01:14 PM
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originally posted by: Zaphod58

In addition to the C-130 having access to rougher strips, a C-17 requires 3,500 feet to operate, if it's extremely light. The C-130 only needs 3,000 feet with a medium load. That's with a 500 foot safety margin added. The J model can takeoff with a heavy load in similar conditions.


Yeah, but TO distances in a fixed-wing aircraft are a function of wing-loading, and not of propulsion type (though you may get small benefits from greater wing area being blown by the props). Rough field ability is a function of loading, speed and gear/tire-performance. Given the same TO weight, there should be little or no difference between a turbo-prop A400M and a turbo-fan version generating the same net thrust.

Main advantages for turboprops are in fuel consumption at non-transonic speed, such as the requirements of the A400M project.


Props have more constant thrust than jet engines so they actually produce more power at low speed.

Ermm, what? It's easier to change available thrust in a turboprop by changing blade pitch and not having to wait for the engine to spool up, but apart from that, I don't have any idea why you would think the static thrust available would be advantageous to a turboprop?



posted on Nov, 3 2015 @ 01:20 PM
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a reply to: RadioRobert

Precisely because you DON'T have to wait for it to spool up like you do a turbofan. You adjust a turbofan and there's a delay, you adjust the pitch of the prop and it's almost immediately at the adjusted power setting.



posted on Nov, 3 2015 @ 01:33 PM
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a reply to: Zaphod58

Right and I alluded to that, but that's not "more constant thrust" producing more power? Not sure what you were getting at



posted on Nov, 3 2015 @ 01:37 PM
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a reply to: RadioRobert

That the thrust of a turboprop is steadier and fairly constant compared to a jet engine. It reacts faster and gives you a better power response especially on a dirt strip. I may not have put it the best way, but the end result is the same. Turboprop engines are better for rough field ops no matter how you slice it.



posted on Nov, 4 2015 @ 12:46 AM
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Mechanical propulsive efficiency is greatest with the lowest exhaust velocity and the greater amount of mass being propelled. Same reason helicopters use blades with extremely large diameter despite not having a power to weight ratio much greater than fixed wing aircraft. Same reason tilt-rotors and STOVL fixed wing struggle.

Spool-up is probably too fast to matter especially when considering holding the brakes.
edit on 4/11/15 by C0bzz because: (no reason given)



posted on Nov, 4 2015 @ 05:24 PM
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a reply to: C0bzz

On takeoff, spool up doesn't matter. But trying to fly low and slow to put down on a short strip, the greater the diameter of your fan, the longer it takes to spool up ( a bit of a generalization because it varies by engine type, but the physics are sound). 5 seconds to spool from flight idle to max doesn't seem like a lot until you're jockeying the throttle trying to put down on a short, unimproved strip with 200,000 lbs of umph behind you or until you misjudge your approach and need to go around.


Re: Mechanical efficiency, you could sort of look at a turbo prop as a larger ultra-high bypass turbojet



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