https://theaviationist.com/2017/08/3...aft-prototype/

Better images from The Aviationist

https://theaviationist.com/wp-conten...-side-view.jpg

0 Deg Nacelle?
 

It is looking fairly close for clearance between stub wing and blades in airplane mode or zero deg nacelle angle? Just an observation.:confused: Otter

0 nacelle is airplane mode. Clearance has been designed to allow more rotor flapping than previous tilt rotors to accommodate the greater maneuverability required by the spec.

0 Deg Nacelle
 

Sultan

Correct, the clearance for the V-22 between blade tip and fuselage is about 10 to 12 inches. If the V-280 has the same clearance the landing gear stub-wing looks like it protrudes from the fuselage at least that far. Maybe the blade tip fuselage station location during airplane mode flight is aft of the landing gear stub-wing? :confused: Ott

Pretty sure they provided adequate clearance between the rotor tip sweep and MLG sponson surface under all anticipated operating load/deflection conditions.

Congratulations to the team on getting started on restrained runs!

As for some of the rotor clearance comments, I'm sure Bell did a lot of work studying that and I have no doubt the rotor will always clear the fuselage. The rotor to wing clearance is trickier since the blade flexibility will allow additional deflection even if the hub has flapped to a hard stop. Blade to wing clearance will likely always rely on the aircraft being inside a known flight envelope and predicted flap, yaw, roll response.

The exposed hardware when the nacelle is in VTOL mode looks vulnerable to bird strike... I understand that as a demonstrator, the certifying authorities might not require bird strike resistance. Something to address in a production version.

"The exposed hardware when the nacelle is in VTOL mode looks vulnerable to bird strike..."

Interesting how that area was blurred-out of the photo and video provided in the article linked by Sultan. There are 3 or 4 published US patent applications covering the related IP dating back to late 2014. Maybe there is something there not yet protected by a patent application.

Maybe... there are a few unblurred photos floating around. I suspect that's the sort of requirement that is more strictly designed for and tested under a production contract.

Been waiting for someone to state the obvious. The area of discussion on bird strike is not exposed except at low speeds at which a strike poses no risk. At speeds that might be worthy of concern the aircraft is fully converted and the area is protected by the nacelle.

It strikes me that with its wingspan coupled with the rotating blades, the V-280 is going to need a very substantial clearing / vessel / landing mat / parking apron from which to operate compared to the current UH-60, or even Sikorsky-Boeing's SB>1. Have tried Googling the V-280's dimensions, but no joy coming up with any measurements (maybe just looking in the wrong place).

It might also have been mentioned already, but surely any forward firing weapons would be inhibited by the V-280's two huge rotor discs (FVL-Medium is after all supposed to replace the Black Hawk and Apache)? The only imagery I have seen of the V-22 firing rockets shows the engines in the 45% angle.

All in all, I think the SB>1 is the far more practical solution (assuming Sikorsky-Boeing can overcome their current technical difficulties).

There is some comparison in a Bell brochure

http://www.bellhelicopter.com/~/medi...shx?sc_lang=en

SLB

Sultan is correct, but even on conventional airplanes and helicopters the aircraft structure provides almost zero system protection from bird strikes. If the structure was strong enough to withstand a 2 lb bird at Vmax and shield all the systems underneath, the aircraft would be to heavy to leave the ground. Instead critical systems are installed in locations behind massive components (like gearboxes) or sacrificial components (like non critical avionics boxes). Where this cannot be accomplished redundant systems are employed with adequate separation to prevent a common mode event effecting multiple systems.

As far as dust and debris entering the open area, have you ever seen the inside of a landing gear bay? Landing gear bays are packed full of wiring, hydraulics, and other systems to provide easy access. And landing gear bays are one of the dirtiest areas on an aircraft. We just design the system installations for the environment.

So why blur out the open area of the pylons? Maybe it is just some marketing executives aesthetic tastes are compromised by the sight of system installations. Personally I am fond of the looks of the skinless Bell 47 that hangs its systems out for the world to see. Beautiful!

Based on a prior Bell graphic, the V-280's specs are as follows:

• Overall length, rotors turning: 51 ft (UH-60 = 65 ft)
• Fuselage length: 51 ft (UH-60 = 50 ft)
• Overall width, rotors turning: 80 ft (UH-60 = 54 ft)
• Rotor diameter: 35 ft (UH-60 = 54 ft)

https://i.imgur.com/FaUZfKh.jpg
(Click for full-size image)

I/C

It's still easy to get surprised by bird strike testing... I saw what a 2.2 lb bird did to rotor controls and spinner supports at only 75 knots. The V-280 in the conversion corridor can go fast enough in near VTOL mode for a bird to do real damage. Obviously not a show stopper like CTR points out, but it's not a requirement you just hand wave away on a production vehicle.

And CTR, I agree, I like the clarity of the skin-less helicopter as well. Got up close to an S-64 once... nothing hidden anywhere and it's beautiful for it.

I haven't been able to find rotor diameter data for the SB>1, but have zero doubt both JMR demonstrators are larger in gross weight and planform than the H-60 and AH-64 aircraft.

Reportedly 50 ft.
...As evidenced by the fact that we're already using 5,000 shp class engines for a platform with a 12-seat cabin. It'll be interesting to see what cabin size is eventually settled upon for FVL-M. As mentioned previously in this thread, some of the FVL squad sizing AoAs - especially those incorporating the use of exoskeletons - have pointed at something far larger than even the JMR AVDs.

I/C

I concur. My friends from the 609 program are the same engineers that oversaw the V-280 system installations, and they followed the same bird strike survivability design requirements as for an FAA certified aircraft.

The XV-15 actually suffered a bird strike to the wing leading edge by a turkey buzzard weighing an estimated 10 lbs that took out the torque shaft connecting the two conversion actuators. Luckily the engineers back then planned for that event and installed a backup system that decluched the shaft. The bird actually passed through the rotor before striking the leading edge.

Maybe this is a slightly naive suggestion...

...but would buying both not be the best option for the US Army? Common engines (I think?), potentially commonality in avionics, but different platforms for different missions. Not to mention, keeping the ability to manufacture military helicopters alive in two rather than one organisation (accepting that each involves multiple players). The SB1 looks like a much better replacement for the Apache than the V280, but on the other hand, the V280 looks very good as a Blackhawk replacement...

Thanks for the link... I assume they meant 25' radius. If that's the case, then a similar pad size to the H-60 platform. You're right, the goals of the various capabilities specifications for the various FVL classes are aggressive and pretty future-looking.