Bin Laden Raid: Why Did the Blackhawk Crash?

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As we all probably did, I watched and read a lot of coverage on the Bin Laden raid a year ago. What caught my eyes and ears was speculation on why the MH-60 Blackhawk crashed when attempting to land in the compound. We may never know the real cause, but the most-reported reason was that the aircraft entered vortex ring state, also known as settling with power.

This little YouTube video explains VRS, but the short course is that it happens when the rotor disc doesn't have enough clean air to generate sufficient lift to keep the aircraft from settling—it can be caught in its own wash or turbulence from surface features. It's the opposite side of the coin from translational lift. VRS is always a risk on the approach to landing.

Viewed from inside, it's a little like parachute mode in a light aircraft; a wobbly state of slow settling. It can be recovered similarly, by reducing the collective and pitching the cyclic forward to increase airspeed to get the disc into clean air. But that takes altitude and if there's not enough of it, a hard touchdown or crash will be the result. This video depicts what appears to be classic VRS. (Watch it to the end.) Sometimes, excess power can arrest the settling, but in this case, the trees intervened. And the heavier the aircraft, the more aggravated the settling. (The MH-60 was equipped with stealth hardware and was probably heavier than a standard Blackhawk.)

During one interview, former CJCS Adm. Mike Mullen said he watched the teams train for the mission in the Nevada desert with an exact mockup of the Bin Laden compound, but with a fence rather than the compound's 12-foot high walls. See the problem? A walled compound acts like a big bowl, reflecting the rotor wash upward and potentially making a mess of roiled air that would make VRS more likely. Since these teams have done these operations in the hundreds, the pilots would have known this, if they knew the target was walled in rather than fenced in. Mullen seemed to indicate that during training, they did not know who or what the target would be until very near the step off date.

That left me wondering if their briefing included information on the walls—I can't imagine it wouldn't have—and if so, did they decide the risk of unrecoverable VRS was low enough to proceed? Did they encounter higher density altitude than expected? Or are they good enough to just scoot in over the wall and plant it? That wouldn't surprise me in the slightest. Helicopter pilots, educate us.

One former spec ops pilot quoted in the Army Times said the stealth Blackhawks are equipped with anti-radar coatings on their windshields that may make it difficult to see with night vision gear. It's possible that VRS wasn't the cause at all, but that the helicopter simply clipped its tail rotor on the wall and lost control. Either way, you have to admire the pilot's training and skill to plant the nose in the dirt to keep a bad situation from getting worse. And to the SEALS for shrugging off the crash they'd just been in and getting on with business.

We should all do our day jobs as well.

Comments (33)

What if the OBL Assassination event is in the same class of event as the Gulf Of Tonkin?

Posted by: Richard Sinnott | May 5, 2012 1:19 PM    Report this comment

In the Gulf of Tonkin, the patrol boats didn't take credit for the raid--Osama did.

He got what was coming to him--just not soon enough.

Posted by: jim hanson | May 5, 2012 4:49 PM    Report this comment

What if it's in the same class of event as the story we were told about Pat Tillman's death? Jessica Lynch's tale?

Discussions of VRS and stealth helicopters (is that an oxymoron, or what?)notwithstanding, the odds are that OBL was dead for years.

I have no doubt there was a raid there, but I seriously doubt that OBL was there. If he had been, they would have returned him to the US and paraded him down Broadway in handcuffs.

Posted by: Richard Sinnott | May 6, 2012 7:59 AM    Report this comment

Ah, same class of tin-foil-hat conspiracy as 911 as an inside job. I get it, while pointing out that both the Tillman and Lynch incidents were soon exposed because the people involved just couldn't keep a secret.

Same deal here. If this was staged, too many people involved in too elaborate a scheme for it not to leak sooner or later. Somehow, I doubt if the current administration is quite that audacious.

You say "odds are OBL was dead for years." And how to you calculate such odds? Data available from conspiracy web sites? Or does stating it make it so?

Anything is possible, I suppose. But often, the simplest explanation is closest to the truth. Let's talk in a few months when the wraps are removed from this conspiracy, as they inevitably will be. (Still waiting on the 911 truthers.)

Posted by: Paul Bertorelli | May 6, 2012 9:16 AM    Report this comment

Mr. Sinnott, what makes you such an expert that you can have "no doubt" about the Abbottabad raid, but also claim that OBL has been "dead for years"? What if, you are just plain wrong? Really, parade him around the US? Please, look at the circus surrounding the Gitmo detainees. It would be 1000 times worse with OBL. Obama did the right thing, shoot on sight, bury at sea. Anyway, here's hoping this conversation starts discussing VRS.

Posted by: Harold Moritz | May 7, 2012 6:32 AM    Report this comment

Besides VRS, a likely issue was marginal HOGE performance. Although no longer at gross after reaching Abbotabad, a quick web search puts UH-60A Black Hawk HOGE ceiling at 5,400 feet (1,645m.). I took a look at current overnight weather for Abbotabad, and the Density Altitude calculates to 5653 feet. Of course, these were not the exact figures for last year, but still, HOGE performance was marginal. So, first, they were right around the HOGE ceiling as they descended, and then, once close enough to the ground for HIGE to rule, they were most likely subject to VRS.

Posted by: Doug Wenzel | May 7, 2012 8:17 AM    Report this comment

Gunfire, RPG, mechanical failure, power lines, pilot error. Stealth or not, helicopters draw a lot of attention to themselves when in a low altitude hover. They are also fragile machines because of their huge spinning disc. All those seem more likely than a freak turbulence event...

Posted by: Mark Fraser | May 7, 2012 8:31 AM    Report this comment

I was taught that there were three conditions necessary for settling with power. A vertical, or near vertical descent, low forward airspeed and some engine power applied. VRS can happen to the main rotor or the tail rotor so settling with power is the more appropriate term. VRS in the tail rotor leads to a condition known as Loss of Tail Rotor Effect, or LTE and I've experienced this effect in both the AH-1F and the OH-58C. The UH-60A numbers are irrelevant since the aircraft on the mission were either modified L or M model MH-60s with more powerful engines, and higher GW and HOGE/HIGE specs. Ground fire can be ruled out since no direct action happened outside the compound and the Quick Reaction Force aboard the MH-47 were not called into action. I believe it was one of two possibilities. Settling with power or a short approach into the confined area striking the tail on the wall. The latter is most likely in my mind based on the size of the confined area, use of NVGs and possibly brown out conditions. Most spec ops aviation approaches are of a nature that the time and conditions necessary to develop settling with power are simply not present long enough to develop the condition.

Posted by: Mark Traylor | May 7, 2012 9:59 AM    Report this comment

As to helicopters being "fragile machines" I must completely disagree. The last 10 years have demonstrated that US helicopters are very robust and tough machines. Most of the dynamic components are designed and engineered to withstand 23mm cannon fire. There have been numerous incidents of direct hits and detonations of RPGs/rockets, cannon fire, missile hits and CFIT and the aircraft have landed safely with some missing large sections of main rotor blades. Fragile they are not!

Posted by: Mark Traylor | May 7, 2012 10:00 AM    Report this comment

It's called Occam's Razor; the most likely theory is the one that has the simplest assumptions but yet still explains all the evidence. Tin hatters tend to load up rather heavy on the assumption part...

Posted by: A Richie | May 7, 2012 10:04 AM    Report this comment

Paul

You may recall that OBL was on kidney dialysis machines, at least according to published CIA reports. Those folks are quite fragile, and I don't think they have dialysis machines that work in caves.

Further, you might not remember but Benazir Bhutto reported OBL as having been killed in late 2001. Within a month or two of her having said that, and the comment was made in a speech related to other matters, she was assassinated.

Other Asian leaders also reported him as dead. Good grief, Bill O'Reilly even claimed it back in 2004, I think it was.

Dialysis patients cannot live without those machines.

Posted by: Richard Sinnott | May 7, 2012 2:09 PM    Report this comment

It's always a good day when I learn something I didn't know about aviation, and the videos and explanations about VRS and settling with power were interesting for me.

Now if I could only understand why the killing of Geronimo was done a year before the election instead of a month before since he was already dead, I would really celebrate.

Posted by: David Miller | May 7, 2012 3:51 PM    Report this comment

You get the picture Dave. ;-)

A close reading of the news headlines in the 30 day period before the raid might reveal some crisis perhaps more important than the election.

Sometimes, things just have a way of hitting the fan, ya know?

It certainly changed the subject, as far as what was in the news and what folks were talking about.

Posted by: Richard Sinnott | May 7, 2012 4:22 PM    Report this comment

Richard, until I can actually see the ice walls that hold the world's oceans in, I'll go right on believing the earth is round. Overwhelming evidence. Something neither the birthers nor you here have presented for antonymous examination.

But I do agree with you, through some posts on this thread, things did find a way of hitting the fan.

Posted by: David Miller | May 7, 2012 5:34 PM    Report this comment

"short approach into the confined area striking the tail on the wall."

I can see the sense of that. Post-raid pictures of the compound show that the wall was topped with nearly two feet of razor wire stitched to angle iron set in the top of the wall. With NVGs, I could see how it would be easy to miss or misjudge.

The other aspect of this I found interesting is that it illustrates the so-called strategic corporal concept. (Or maybe strategic WO in this case.) How the entire success of a mission can pivot on the decisions and actions of one person in a space of a few seconds. If the pilot hadn't controlled the crash--assuming he did--the outcome could have been very different.

Posted by: Paul Bertorelli | May 8, 2012 6:42 AM    Report this comment

Dave

I too believe the earth is round. Never heard of those ice walls you mention.

I guess the difference between you and Paul and me is that I am unable to muster the same presumption of veracity towards government press releases that you and Paul seem to possess. Probably has to do with my old age.

Posted by: Richard Sinnott | May 8, 2012 7:36 AM    Report this comment

VRS seems the less likley of the proposed causes. For the main rotor to get into developed VRS requires a descent rate approaching the downwash velocity of the MR. For a large, heavy helicopter with high disk loading, this could significantly exceed 1000 FPM. Possible but seems unliklely under the published circumstances.

Posted by: R Boswell | May 8, 2012 3:22 PM    Report this comment

"VRS is always a risk on the approach to landing."

Not really provided descent rate is well below downwash velocity - easily done in most helicopters.

"by reducing the collective and pitching the cyclic forward to increase airspeed to get the disc into clean air" Getting into clean air is key and moving the cyclic left, right or aft (as well as forward) can also facilitate this.

Posted by: R Boswell | May 8, 2012 5:21 PM    Report this comment

...I am unable to muster the same presumption of veracity towards government press releases that you and Paul seem to possess. Probably has to do with my old age.'

Richard, would age prevent you from accepting the press releases about a recession, an election result, a bill passage in Congress, the unemployment figures, warnings or foiling of a terrorist threat, a CDC warning of a virus, your Social Security check being delayed, or separation instructions from ATC? This entire thread is a result of a government press release for discussing exactly how a Blackhawk went down. Or did it?

What if government was the size you wanted it to be, the deficit was nil, and your political party was in power. Trust it then? What really makes the difference?

I suggest a trip to one of our fantastic National Parks, or the Smithsonian for some balm against all the cynicism rampant today. Or visit a VA hospital with some magazines under arm for the Vets. You're never too old for them.

Posted by: David Miller | May 8, 2012 10:14 PM    Report this comment

As an agent for a military organisation in a now defunct country I would like to say that I believe the attack took place but all indication tell me there were alternative motive for the attack. Someone was assassinated but who? we are all still guessing. My experience tells me that when a story does not lie down and die there is something else in it. The moon landings are an example I believe that they all took place and man did get to the moon but there is something on the moon that is being kept secrete and as long as the conspirators shouting about their disbelief and keep our eyes off the real issue we will never find out. The same is I believe true here. Did the helicopter crash and why did it seems part of the problem with the belief that OML was assassinated.

Paul it is this type of reporting that sets in motion the truth behind the stories and I applaud you for raising this subject. The real issue is the lack of information to base an accurate account of what did happen. Because the question has been raised I believe those in the know could be forced to come forward and explain what really happened and we need to keep the pressure up and the conspirators out so we can proceed to get what we want to know.

Posted by: Bruce Savage | May 9, 2012 4:31 AM    Report this comment

Are these comments from those who vote against their own self interest and then blame the system they got for all of the bad results?

Posted by: Larry Fries | May 9, 2012 5:22 AM    Report this comment

Good grief. Let me clarify why I raised this issue. It was simply because I am curious about the challenges helicopter pilots face when conducting such operations in tight confines, at night in places they've never seen.

I'm not attempting to raise doubts or sow conspiracy theories about why the MH-60 crashed, but to merely illuminate the various technical issues involved. Nothing more or less. Further, to fake this raid and to claim Bin Laden was killed when he actually wasn't would require a scheme so elaborate as to assure exposure. It would also require the active cooperation of the spec ops people themselves in erecting what is, in the end, a deceit purely for political purposes. (I guess, for I can't imagine any other reason for such extraordinary efforts.) Somehow, I just get the impression they wouldn't go along with such a thing.

And Dave, I'll have you know I have pictures of the ice walls holding the water in. But the ice is so clear, you can't make it out, so you have to take it on faith.

Posted by: Paul Bertorelli | May 9, 2012 5:46 AM    Report this comment

Paul my apologies if you thought I was trying to say you were a conspirator. Far from it. Apparently there was an accident involving a helicopter and if so why the secrecy? Could the accident have taken place? Again we have a lack of evidence of what took place and there are too many variables to accurately determine that eventuality. Could the MH-60 simply had an engine failure, or the pilot was disabled in some way? Could one of the rotors hit an object (aerial) that was not foreseen? And yes all assignation are for political reasons

Hello Mr Fries nice to hear from you again ;-)

Posted by: Bruce Savage | May 9, 2012 6:21 AM    Report this comment

As a former Army helo pilot who flew Hueys, OH-58s and Cobras I doubt it was "settling with power." We were taught about this in flight school but I never got close to it in actual operation and didn't experience anyone else in our unit doing it either. Hueys were vastly underpowered compared to today's Blackhawks. I think the pilot just made a mistake and hit the wall with the tailboom. Understandable under the circumstances. Fortunately they were prepared and everyone got out. Stuff happens and although I kind of hate to say it but helos are inherently dangerous and demand constant attention. They are very unforgiving of even slight mistakes.

Posted by: larry maynard | May 9, 2012 6:58 AM    Report this comment

I agree completely with Larry Maynard.

Paul, with all considerable and due respect, perhaps you might choose your titles more precisely next time. If you want to discuss aerodynamics and operational considerations, stick to that.

If you choose to analyze or incorporate a political story into your blog, expect comments like mine. I'm happy to discuss helicopter aerodynamics, but I'm not going to embrace by innuendo what in all probability is another government fable in order to do so.

Beware inadvertant political statements.

Posted by: Richard Sinnott | May 9, 2012 7:17 AM    Report this comment

Until the 1980s, when night-vision goggles were developed --really nasty things which guaranteed a splitting headache after half hours use -- helicopters could not fly at night because the pilots could not see the horizon. Even now, with 30 years of extra technology, flying a helicopter at night is very difficult, and the goggles still give splitting headaches. Add to that the fact you train to jump over fences and not walls, and probably were not told about the angle iron on the top of the wall anyway, and it is a recipe for disaster. Too many generals watching too many movies, plus too much boasting, make special forces accept silly odds. They were very lucky this time.

Posted by: Brian McCulloch | May 9, 2012 8:20 AM    Report this comment

How about this: Why Did the Blackhawk Crash (Note: This headline isn't meant to imply, suggest or impugn the existence of any kind of conspiracy. Please do bother to actually read the blog before commenting. )

It's a little long, but I can work on the concision. Thanks for the suggestion.

Posted by: Paul Bertorelli | May 9, 2012 8:24 AM    Report this comment

Richard: "perhaps you might choose your titles more precisely next time." The title is "Bin Laden Raid: Why Did the Blackhawk Crash?" I don't see how to make it clearer and less political. "Bin Laden Raid" defines the event, "Why Did the Blackhawk Crash?" defines the subject being discussed. Classic journalism -- I don't see how it could have been done better with fewer words. Don't blame Paul for your own actions - he set the focus on the technical, you chose to change the focus to the political. Next time stick to the subject.

Posted by: Jonathan Spencer | May 9, 2012 8:35 AM    Report this comment

Paul,

Judging from the quantity of off-topic posts here, it appears that there is merit in creating a separate blog dedicated to speculation, hearsay, and unprovable positions about the bin Laden operation.

Such a blog might clear the room of the conspiracy theorists, religionists, and others unable to accept science as the basis of knowledge, and allow the rest of us to get on with substantive discussion about vortex ring state.

Posted by: Gordon Mano | May 9, 2012 9:51 AM    Report this comment

Geez, I understood this to be an AVIATION related topic not this other crap. For Brian McCulloch, I don't know your background or operational NVG experience, but I know what mine is and I can say this for a fact. I flew NVG missions one to two nights a week from 2008-2010 for 3-4 hours a night. Not one headache from NVG use. Tired neck, yes. Headaches no.

Posted by: Mark Traylor | May 9, 2012 10:00 AM    Report this comment

Yes Paul, the title itself is excellent. The parenthetical material is a bit verbose and unnecessary.

Considering that all we have is a picture of a wrecked helicopter, our examination can only be superficial and speculative.

Or, did I miss any statements from the pilots, the weather including DA and prevailing winds at the time of the crash?

So are we able to make an accurate assessment with the information we have? No.

As for the political implications, they are there, intended or not. This is, after all, the Age of the Internet.

I think a better discussion might be about the stealth technology that was employed. Is 'stealth' a relative term? How can one overcome the radar return implications on a set of turning rotor blades?

Posted by: Richard Sinnott | May 9, 2012 10:22 AM    Report this comment

Mark, Larry, clarify something for me. Some explanations of settling with power I've seen suggest that it's the same as VRS for the main rotor.

But you seem to indicate they are different phenomenon. What's the training doctrine on this?

Posted by: Paul Bertorelli | May 9, 2012 12:30 PM    Report this comment

Thanks for saving me the trip, Paul. If they're that clear I won't know how high to climb to avoid them so I guess that rules out LSA space flight for me.

Mark Traylor, sometimes the best aviation topic can slide into side discussions that also I find can be interesting and informative. The bloggers are usually tolerant and understanding of that. But when things go to conspiracy theories, or criticizing others and that kind of crap, I agree it's probably getting away from the subject and redirection is appropriate.

Posted by: David Miller | May 9, 2012 2:16 PM    Report this comment

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