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-   -   Sikorsky SB-1 flies for first time (https://www.pprune.org/rotorheads/619699-sikorsky-sb-1-flies-first-time.html)

etudiant 12th May 2021 20:37

I've zero expertise in this area, but a recent comment in a defense publication caught my eye.
It claimed the SB-1 was preferable because its rotor diameter was similar to that of the UH-60, allowing use of common landing zones.
This seemed somewhat over the top to me (or possibly clutching at straws).
Can anyone with experience in this space provide some insight please?

CTR 12th May 2021 22:21

Check out Commander Cody’s earlier post.
 
[isQUOTE=Commando Cody;11007479]FWIW, here's a comparison of the footprint of the V-280 vs. UH-60


https://cimg1.ibsrv.net/gimg/pprune....095f2b39fe.jpg[/QUOTE].

Check out Commander Cody’s earlier post

SplineDrive 12th May 2021 23:32


Originally Posted by CTR (Post 11043541)
[isQUOTE=Commando Cody;11007479]FWIW, here's a comparison of the footprint of the V-280 vs. UH-60


https://cimg1.ibsrv.net/gimg/pprune....095f2b39fe.jpg

.

Check out Commander Cody’s earlier post[/QUOTE]

And since Sikorsky hasn’t released a rotor diameter, here is a top down photo of SB>1 and an H-60 for visual comparison. There’s a difference in footprint between them all, but it’s largely the orientation of the aircraft that’s different, not the area itself.

(The red circles are the same, looks like SB>1 rotor diameter is ~3 feet larger in area than an H-60?)
https://cimg1.ibsrv.net/gimg/pprune....145ce0262.jpeg


henra 14th May 2021 18:12


Originally Posted by SplineDrive (Post 11043567)

Interesting!
Looking at the two footprints I'm wondering a bit if cabin volumes between the two are comparable by any means?!. While the fuselage of the V280 looks markedly slimmer than the Blackhawk, SB-1 looks MASSIVE compared to it.

CTR 14th May 2021 20:30


Interesting!
Looking at the two footprints I'm wondering a bit if cabin volumes between the two are comparable by any means?!. While the fuselage of the V280 looks markedly slimmer than the Blackhawk, SB-1 looks MASSIVE compared to it.
Not surprising when you consider that on the V-280 the fuselage only needs to hold the crew and passengers.

Compared to the SB>1 fuselage which must house engines, gearboxes, fuel, in addition to crew and passengers.

henra 14th May 2021 21:07


Originally Posted by CTR (Post 11044758)
Not surprising when you consider that on the V-280 the fuselage only needs to hold the crew and passengers.

Compared to the SB>1 fuselage which must house engines, gearboxes, fuel, in addition to crew and passengers.

I was referring more to the width of the fuselage. While the V280 fuselage is narrower than the UH-60, the SB1 appears to be much wider. Length of the cabin obviously can't be determined from the overhead shot.
So it might be that V280 has a long but narrow cabin while SB1 has a wider but shorter one.
It seems I haven't seen cabin dimensions of the two so far. Any numbers out there in the wild?

CTR 16th May 2021 16:27


Originally Posted by henra (Post 11044775)
I was referring more to the width of the fuselage. While the V280 fuselage is narrower than the UH-60, the SB1 appears to be much wider. Length of the cabin obviously can't be determined from the overhead shot.
So it might be that V280 has a long but narrow cabin while SB1 has a wider but shorter one.
It seems I haven't seen cabin dimensions of the two so far. Any numbers out there in the wild?

No cabin dimensions for either aircraft I can find. But lots of photos of seating layouts for mock-ups and artist renderings. Based on seating layout of the V-280, the cabin appears to be longer and narrower than the SB>1.
https://cimg9.ibsrv.net/gimg/pprune....b5bf47eed.jpeg
https://cimg0.ibsrv.net/gimg/pprune....490f65587.jpeg

While both seating layouts have benefits and compromises, I find it odd the SB>1 layout does not have provisions for the side gunners like the V-280.

noneofyourbusiness 21st May 2021 16:45

Fuel burn - Let's say a fully loaded V-280 cruises at 280 knots. A fully loaded Defiant maybe 220? knots. Because the Defiant is slower, that makes its fuel burn look better than it really is. A fixed wing provides 15? lbs of lift per lb of thrust - a clear advantage for the V-280 Valor. Does Defiant have to carry more fuel to meet the Army range requirements? That would be a significant penalty, both in terms of weight, and in fuel cost.

A twin main rotor design has more drag than a single main rotor design. The close spacing of the rotors is intended to minimize this extra drag. This extra drag can be overcome with brute force, but this means burning more fuel. The same applies to the FARA program. Does DOD want to procure high fuel burn aircraft for the next 30 years?

SplineDrive 21st May 2021 19:59


Originally Posted by noneofyourbusiness (Post 11048741)
Fuel burn - Let's say a fully loaded V-280 cruises at 280 knots. A fully loaded Defiant maybe 220? knots. Because the Defiant is slower, that makes its fuel burn look better than it really is. A fixed wing provides 15? lbs of lift per lb of thrust - a clear advantage for the V-280 Valor. Does Defiant have to carry more fuel to meet the Army range requirements? That would be a significant penalty, both in terms of weight, and in fuel cost.

Defiant-X definitely has a lower cruise efficiency (L/De) than V-280 but actual fuel consumed also depends on cruise speed and engine SFC, etc. They appear to have been successful in talking down the speed requirement which would also reduce the power required to cruise. Is it enough lower to overcome the poor L/De (relative to a tilt rotor) and require less fuel to cover the same distance as V-280 but at lower speed? Unknown. Could well be slower AND take more fuel to meet the mission radius. They haven’t said what engine Defiant-X will use and that’s an important variable in the question.

Of course, Defiant (nor Raider) can hit 230 knots in level flight, despite that speed being inside design requirements for both demonstrators. So we’re discussing the fuel efficiency of a solution that hasn’t been shown to meet the speed requirement, regardless of power/fuel consumed.

Commando Cody 24th May 2021 23:35

Regarding cabins of the two, something became apparent around the time they were engineering the X2 demonstrator: I guess because of the space the mast and transmission needs, on an X2 all of the cabin has to be forward of that location. So the SB>1/Defiant-X cannot use as much of it fuselage length as could a conventional helicopter or Tilt-Rotor. This would drive them to a wider cabin.



etudiant 24th May 2021 23:40

Whatever the reason, this thing is huge. It will make a great target, based on the ponderous 'agility' demonstration video aired earlier.

noneofyourbusiness 25th May 2021 16:24


Originally Posted by Commando Cody (Post 11050783)
Regarding cabins of the two, something became apparent around the time they were engineering the X2 demonstrator: I guess because of the space the mast and transmission needs, on an X2 all of the cabin has to be forward of that location. So the SB>1/Defiant-X cannot use as much of it fuselage length as could a conventional helicopter or Tilt-Rotor. This would drive them to a wider cabin.

A wider fuselage means more airframe drag.

casper64 25th May 2021 22:12


Originally Posted by noneofyourbusiness (Post 11048741)
Fuel burn - Let's say a fully loaded V-280 cruises at 280 knots. A fully loaded Defiant maybe 220? knots. Because the Defiant is slower, that makes its fuel burn look better than it really is. A fixed wing provides 15? lbs of lift per lb of thrust - a clear advantage for the V-280 Valor. Does Defiant have to carry more fuel to meet the Army range requirements? That would be a significant penalty, both in terms of weight, and in fuel cost.

A twin main rotor design has more drag than a single main rotor design. The close spacing of the rotors is intended to minimize this extra drag. This extra drag can be overcome with brute force, but this means burning more fuel. The same applies to the FARA program. Does DOD want to procure high fuel burn aircraft for the next 30 years?

The question remains: how important is all this “cruise” stuff.... you can take a Hercules for that part. For a tactical helicopter you need surviveability, agility, low costs, small footprint, good OGE power margins, low, easy maintenance... that kind of stuff and yes maybe a bit quicker than the one it is replacing....

SansAnhedral 26th May 2021 00:30


Originally Posted by casper64 (Post 11051407)
The question remains: how important is all this “cruise” stuff.... you can take a Hercules for that part. For a tactical helicopter you need surviveability, agility, low costs, small footprint, good OGE power margins, low, easy maintenance... that kind of stuff and yes maybe a bit quicker than the one it is replacing....

How exactly do you plan an air assault mission to land a Hercules without an airstrip? That argument falls flat on its face instantaneously.

You also forgot about range, unsurprisingly. That has exponential cascading effects on logistical footprint.

CTR 26th May 2021 03:00


Originally Posted by casper64 (Post 11051407)
The question remains: how important is all this “cruise” stuff.... you can take a Hercules for that part. For a tactical helicopter you need surviveability, agility, low costs, small footprint, good OGE power margins, low, easy maintenance... that kind of stuff and yes maybe a bit quicker than the one it is replacing....

Based on your post, I can’t understand what point you are trying to make. What evidence do you have that the Defiant can eventually achieve any of the attributes you listed? Especially in lieu of Sikorsky and Boeing success rate to date on proving Defiant capabilities in flight test.


Commando Cody 26th May 2021 21:11


Originally Posted by casper64 (Post 11051407)
The question remains: how important is all this “cruise” stuff.... you can take a Hercules for that part. For a tactical helicopter you need surviveability, agility, low costs, small footprint, good OGE power margins, low, easy maintenance... that kind of stuff and yes maybe a bit quicker than the one it is replacing....


What "cruise" gets you is less time exposed to enemy fire en-route, Also the ability to operate higher, out of the range of light weapons. It allows you to do more with less assets and with fewer required bases because the reduced transit times mean you need fewer assets in total and fewer bases since the vehicles can get there in the same time from twice as far away.

Al of the other things you mentioned are already incorporated int the requirements, they've always been there. What newer technology buys is all that plus greater speed, range, responsiveness, versatility and effectiveness.

JohnDixson 27th May 2021 16:50

CV-22 Crew
 
Anyone notice that on the Osprey thread, the latest post #642 refers to the last CV-22 being delivered at Cannon AFB to its "two assigned crewchiefs".Typo??

Commando Cody 27th May 2021 19:48


Originally Posted by JohnDixson (Post 11052526)
Anyone notice that on the Osprey thread, the latest post #642 refers to the last CV-22 being delivered at Cannon AFB to its "two assigned crewchiefs".Typo??

CV-22B normally flies with crew of four: pilot, co-pilot and two either "crew chiefs" or "flight engineers", depending on the source from which you get the information.

mckpave 28th May 2021 19:41


Originally Posted by JohnDixson (Post 11052526)
Anyone notice that on the Osprey thread, the latest post #642 refers to the last CV-22 being delivered at Cannon AFB to its "two assigned crewchiefs".Typo??

Referencing the Maintenance Squadron comments in the press release this is correct, there are two crew chiefs assigned to each airplane, a primary "dedicated" one, and an assistant CC. They are not flight crew members. The airplane becomes their responsibility for airworthiness, thereby giving them "ownership" in a sense.

SplineDrive 28th May 2021 20:17


Originally Posted by noneofyourbusiness (Post 11051267)
A wider fuselage means more airframe drag.

Wider fuselage also means more of the rear prop is occluded and not all the airflow entering the prop from the fuselage is going to be very predictable. Perhaps this is part of the speed deficit of Raider and Defiant? The X-2 demonstrator was a skinny dart of an airframe by comparison.

In any case, is it just me, or does anyone else see this thread pop up and read it as "Sikorsky SB-1 flies for last time"?


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