Free Republic
Browse · Search
News/Activism
Topics · Post Article

Skip to comments.

The (Stealth) Blackhawk Crash
AvWeb ^ | 5/12/2011 | The AVweb Editorial Staff

Posted on 05/12/2011 7:58:29 AM PDT by BwanaNdege

The (Stealth) Blackhawk Crash The reason a stealthy version of the MH-60 Blackhawk crashed during the May 1 raid that killed Osama bin Laden includes the vortex ring state phenomenon, according to officials, but helicopter crashes in the Middle East are far from uncommon. Hot air close to the ground and the aircraft's proximity to the high walls of the compound could have caused that thin, hot air to be driven by propwash up the walls and then down through the rotor, causing the vortex ring state. With those conditions, the helicopter would have lost lift and settled with power, which is what officials say happened. The resulting hard landing immediately altered the original plan for SEALS to fast rope to the ground from a hovering aircraft. They fared better than they might have. In Iraq, only IED explosions and being shot by the enemy rank higher than U.S. helicopters for killing American soldiers, according to the Armed Forces Journal. And 80 percent of the helicopter accidents occur without the intervention of hostile forces. That said, the military helicopter crash rate is actually better than that of GA aircraft.

The non-hostile, non-combat accident rate for military helicopters currently stands near 2.1 per 100,000 hours while flying in some of the least hospitable conditions available to helicopters. Meanwhile, the accident rate for GA aircraft stands at 6.86 per 100,000 hours. The military helicopter pilots are most often brought down due to a combination of weather conditions and terrain. Night vision goggles have improved matters, but dust storms, brownouts caused by rotor wash, wire strikes and controlled flight into terrain are still problems the military and Congress hopes to better address. Proposed fixes include terrain avoidance avionics that would warn pilots of potential hazards. (cont)

(Excerpt) Read more at avweb.com ...


TOPICS: Foreign Affairs; News/Current Events; Technical; War on Terror
KEYWORDS: crash; helicopter; operationgeronimo; osamabinladen; pakistan; specialforces
This sounds about right. According to Google Earth, the elevation of the compound is 3900 feet. Here is a description of "settling with power" or "vortex ring state". "http://en.wikipedia.org/wiki/Settling_with_power "

I've only encountered it twice, both times above 4500 feet when trying a high hover & backwards flight while filming a moving train. thankfully, I had enough altitude to dive out of the descending column of air and regain lift.

1 posted on 05/12/2011 7:58:32 AM PDT by BwanaNdege
[ Post Reply | Private Reply | View Replies]

To: BwanaNdege

http://en.wikipedia.org/wiki/Settling_with_power


2 posted on 05/12/2011 7:59:55 AM PDT by BwanaNdege ("Experience is the best teacher, but if you can accept it 2nd hand, the tuition is less." M Rosen)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BwanaNdege

That makes sense. I wonder if the fact that it was a “stealth” helicopter makes any difference as far as losing lift is concerned?


3 posted on 05/12/2011 8:04:55 AM PDT by smokingfrog ( sleep with one eye open ( <o> ---)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BwanaNdege

This was discussed in some publications earlier. The stealth birds are heavier, harder to see out of, and would have been coming in pushing max weight capacity. Still, I’d hate to be the pilot of that bird.


4 posted on 05/12/2011 8:06:33 AM PDT by moehoward
[ Post Reply | Private Reply | To 1 | View Replies]

To: smokingfrog
I wonder if the fact that it was a “stealth” helicopter makes any difference as far as losing lift is concerned?

I don't know much about helicopters, and even less about "stealth" helicopters, but 30 years of engineering intuition tell me that whatever they're doing to make that machine stealthy is probably not helping it's flight characteristics.

5 posted on 05/12/2011 8:09:51 AM PDT by Steely Tom (Obama goes on long after the thrill of Obama is gone)
[ Post Reply | Private Reply | To 3 | View Replies]

To: BwanaNdege

It might “sound right” but consider that the aviators of the 160th Aviation Regiment (Night Stalkers) would have anticipated this and planned accordingly. My guess — and it is a guess — is that the chopper was ‘sacrificed’ as part of the tactical assault plan.

If they really were planning to fast-rope there likely would have been a lot of injuries among the passengers. I’m thinking everybody was strapped in anticipating a hard landing — a la the Son Tay raid (Vietnam).

You run a chopper into a walled compound & assault from the inside out.

I could be wrong because of 2 factors — we left a significant portion of the chopper intact, and (2) there was no followup airstrike to waste what was left.


6 posted on 05/12/2011 8:13:16 AM PDT by Tallguy (Received a fine from the NFL for a helmet-to-helmet hit.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BwanaNdege

I saw footage of one of those Sikorsky Sky Cranes do a that a few years ago. He was operating for a logging outfit, tried to land in a small field surrounded by tall trees. Slammed in pretty hard.


7 posted on 05/12/2011 8:13:48 AM PDT by Thermalseeker (The theft being perpetrated by Congress and the Fed makes Bernie Maddoff look like a pickpocket.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Steely Tom

The Stealth treatment probably slowed max airspeed and the changes to the tailrotor probably affected anti-torque authority, but hover lift should not have been affected, unless main rotor blade tip changes screwed thing up.


8 posted on 05/12/2011 8:14:51 AM PDT by BwanaNdege ("Experience is the best teacher, but if you can accept it 2nd hand, the tuition is less." M Rosen)
[ Post Reply | Private Reply | To 5 | View Replies]

To: BwanaNdege

From a picture in the compound it looked like the tail section landed on a wall. Whether that was due to pilot error or a malf is not known.


9 posted on 05/12/2011 8:17:32 AM PDT by Hacklehead (Liberalism is the art of taking what works, breaking it, and then blaming conservatives.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: moehoward

I got the impression by reading at Aviation Week that is was far from certain that the helicopter was truly some form of advanced, “stealth” helicopter. Covering the tail rotor has been applied elsewhere and the use of anti-IR paint is nothing special.

It may well be a stealth helicopter, but the evidence we have is not sufficient to reach this conclusion. Aviation Week tends to be a quite reliable source in the aviation industry, so I would definitely take the stealth claims with a grain of sale.


10 posted on 05/12/2011 8:17:43 AM PDT by Fractal Trader
[ Post Reply | Private Reply | To 4 | View Replies]

To: smokingfrog

Consider the EH-101 with its advanced rotors.

Its rotors are configured to provide the most lift at the tips, which has been reported to decrease rotor wash and mitigate RVS/Settling. With the greater lift at the rotor tips, the rotor speed is decreased and the rotors may not need to break the sound barrier - sound reduction (one component of “stealth”). That also means less torque (due to lower rotor speeds) and may account for the smaller tail rotors seen in the wreckage photos.

If, as has been suspected, the modified Blackhawk was outfitted with such rotors, I would think that RVS/Settling would less of a concern, but not impossible.


11 posted on 05/12/2011 8:23:34 AM PDT by SJSAMPLE
[ Post Reply | Private Reply | To 3 | View Replies]

To: BwanaNdege

According to the article referenced in your earlier post, vortex ring state results from “upflow” near the rotor mast and blade grip region, a region of the rotor disk that provides no lift. When hovering, this region of the disk can stall; vortices shed by the stalled parts of the blades can propagate toward the outer circumference of the blade disk and disturb lift and control authority.

If they have to put strict limits on blade tip speed for stealth purposes, this problem would be exacerbated, I should think. Add in the environmental and load factors listed above, and it’s fortunate the pilot was skillful enough to save the mission, if not the helicopter.

I believe this is the phenomenon that resulted in the loss of several V-22 aircraft, including one crash that cost the lives of 19 Marines.


12 posted on 05/12/2011 8:25:12 AM PDT by Steely Tom (Obama goes on long after the thrill of Obama is gone)
[ Post Reply | Private Reply | To 8 | View Replies]

To: Fractal Trader

Some reports were it was more of a “modified” model. That tail section though, indicates some fairly serious modification.


13 posted on 05/12/2011 8:27:59 AM PDT by moehoward
[ Post Reply | Private Reply | To 10 | View Replies]

To: BwanaNdege

I love you.


14 posted on 05/12/2011 8:32:21 AM PDT by Lazamataz (The Democrat Party is Communist. The Republican Party is Socialist. The Tea Party is Capitalist.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BwanaNdege

Interesting. If I ever got shot down though, I’d sure set her inside those walls.


15 posted on 05/12/2011 8:33:03 AM PDT by BerryDingle (I know how to deal with communists, I still wear their scars on my back from Hollywood-Ronald Reagan)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BwanaNdege

I wonder if the fact that this was a super secret helicopter and that it is probably brand new left the pilot with very limited flight time with it. That would leave the pilot without the experience to overcome or avoid this type of phenomenon.


16 posted on 05/12/2011 8:39:58 AM PDT by Lazlo in PA (Now living in a newly minted Red State.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BerryDingle

I still don’t understand why that tail was left behind for our enemies to study. Were they taking fire from outside the compound? Seems like it should have been fairly easy to blow up.


17 posted on 05/12/2011 8:40:34 AM PDT by Slump Tester (What if I'm pregnant Teddy? Errr-ahh -Calm down Mary Jo, we'll cross that bridge when we come to it)
[ Post Reply | Private Reply | To 15 | View Replies]

To: BwanaNdege

Isn’t the real point of this that the Pakis may have recovered this and already handed it over to the ChiComs?


18 posted on 05/12/2011 8:44:00 AM PDT by LS ("Castles made of sand, fall in the sea . . . eventually." (Hendrix))
[ Post Reply | Private Reply | To 1 | View Replies]

To: Slump Tester
I still don’t understand why that tail was left behind for our enemies to study. Were they taking fire from outside the compound? Seems like it should have been fairly easy to blow up.

The guys might have been in a bit of a rush when they left. They did their best in the time they had, which was probably about thirty seconds.

Rules of engagement may have inhibited bombardment options from the air. Can you just imagine the response from that team of nitwits in the WH Situation Room when some bomber pilot, orbiting nearby, offered to drop 500 pounders on the wreck?

19 posted on 05/12/2011 8:45:06 AM PDT by Steely Tom (Obama goes on long after the thrill of Obama is gone)
[ Post Reply | Private Reply | To 17 | View Replies]

To: Tallguy
According to ABC's 20/20, the pilot of the chopper that crashed experienced difficulties, tried to raise the bird, then crashed OUTSIDE the wall. The second pilot made a split second decision to land nearby. The SEALS then had to blast though the outer wall.

Consider the source but that was their report.

20 posted on 05/12/2011 8:45:31 AM PDT by SoCal Pubbie
[ Post Reply | Private Reply | To 6 | View Replies]

To: BwanaNdege

How about coaxial rotors? that would cure the close ground vortex and eliminate the need for a tail rotor system.


21 posted on 05/12/2011 9:25:16 AM PDT by Cheetahcat ( November 4 2008 ,A date which will live in Infamy.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: SoCal Pubbie
The SEALS then had to blast though the outer wall.

If you ever come across a photo of a breaching hole, please let me know because I still haven't seen one.

22 posted on 05/12/2011 9:28:04 AM PDT by fso301
[ Post Reply | Private Reply | To 20 | View Replies]

To: fso301
Like I wrote on my post, that's what was stated was in the 20/20 report. They also stated that the power went out in the neighborhood at the time of the raid. There's been so many version of went down that one wonders what the truth is.
23 posted on 05/12/2011 9:31:07 AM PDT by SoCal Pubbie
[ Post Reply | Private Reply | To 22 | View Replies]

To: Steely Tom
I believe this is the phenomenon that resulted in the loss of several V-22 aircraft, including one crash that cost the lives of 19 Marines. One V-22 was lost primarily to VRS at Marana, AZ in April, 2000. Following a long and detailed high rate of descent test program, it was learned that the V-22 VRS margin is actually greater than most conventional helicopters. One has to exceed 2400 FPM ROD to encounter torque bumps and roll-off. And tilting the nacelles forward forestalls VRS, whereas helicopters must drop the nose, lower collective, and fly out of the vortex. TC
24 posted on 05/12/2011 9:42:52 AM PDT by Pentagon Leatherneck
[ Post Reply | Private Reply | To 12 | View Replies]

To: Pentagon Leatherneck; BwanaNdege

Thanks for the info, and for other things as well, both of you.


25 posted on 05/12/2011 9:53:18 AM PDT by Steely Tom (Obama goes on long after the thrill of Obama is gone)
[ Post Reply | Private Reply | To 24 | View Replies]

To: BwanaNdege

“Hot air close to the ground and the aircraft’s proximity to the high walls of the compound could have caused that thin, hot air to be driven by propwash up the walls and then down through the rotor, causing the vortex ring state. With those conditions, the helicopter would have lost lift and settled with power, which is what officials say happened.”

A close friend who does know, and is in a position to know something about all this, says that the size of the opening of the compound and its high walls (& the altitude and air temperature) could have by themselves caused loss of lift, without the vortex ring state - simply collectively restricting how much air could be sucked how quickly under the main rotors, to provide, or to continue to provide the lift. He does not discount the vortex ring theory; he just thinks it is not the only possibility.


26 posted on 05/12/2011 3:18:42 PM PDT by Wuli
[ Post Reply | Private Reply | To 1 | View Replies]

To: Fractal Trader
"I got the impression by reading at Aviation Week that is was far from certain that the helicopter was truly some form of advanced, “stealth” helicopter. Covering the tail rotor has been applied elsewhere and the use of anti-IR paint is nothing special."

I know someone who KNOWS the Blackhawks; intimately. He says the tail rotor size and shape was "non-standard" for a "production" Blackhawk.

If the changes were actually stealth related, the tragedy is not the mere fact that it was left in the compound, but that in all likelihood it has left Pakistan, for China.

Make your own comparisons:

A tour from the maker of the Blackhawks (it's an Adobe Flash video and it starts slow). What is nice is it lets you alter the view of an operating Blackhawk, to see it from either side or either end; at:

http://www.sikorsky.com/Products/Helicopter+Tour

versus

http://cencio4.wordpress.com/2011/05/03/mysterious-helicopter/

which includes the comment:

"However, the depicted horizontal stabiliser and tail rotor of the wreckage don’t seem to be a any form of H-60. Both the shape and position are not common to either Black Hawks or Apaches helicopters. Noteworthy, the tail rotor has a weird cover that could be anything from a stealth cover, to an armour plate to a noise reduction device."

27 posted on 05/12/2011 3:49:41 PM PDT by Wuli
[ Post Reply | Private Reply | To 10 | View Replies]

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
News/Activism
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson