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CZAR 52 Accident

Old 10-05-2010, 09:11 PM
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i am doing a university assignment on a B-52 aircraft accident, the CZAR 52 Fairchild accident to be more precise. The assignment requires us to look at this accident from an aerodynamic perspective and im struggling tying all the elements together to prove what i think happened. I understand the aircraft used spoiler deflection to initiate a roll movement, however it kept rolling to the point where it overbanked, the wings stalled, lost lift and the aircraft crashed to the ground, as a very basic description.
However I'm struggling to support this, using the aircrafts aerodynamics, how it uses spoiler deflection to roll, its swept wings, adverse yaw, sideslip, overbanking, why bank angle continued to increase, roll rate. any help is much appreciated.

Thanks for your time
Daniel
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Old 10-05-2010, 11:11 PM
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anyone?
any help would be much appreciated..
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Old 10-06-2010, 06:05 AM
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Originally Posted by inter09 View Post
anyone?
any help would be much appreciated..
Just a couple quick notes...

Most aircraft use ailerons to turn. Ailerons work by increasing lift in an upward direction on one wing and increasing lift in a downward direction on the other wing. The B-52 uses spoilers. Spoilers "spoil" or kill lift. In the fatal left hand turn of Czar 52, the left spoiler would have been fully raised (causing maximum lift kill on the left wing), while the right spoiler would have been flush. As bank angle increases, so does stall speed. So at the airspeed being flown during the turn, there was a point that the stall speed was greater than the aircraft speed, causing both wings to stall. At this point, the pilot(s) were probably trying to return to level flight with right yoke input. This would have lowered the left spoiler and raised the right spoiler. Also keep in mind, that it takes the B-52 hydraulics several seconds to go from full spoiler deflection on one side to full spoiler deflection on the other side. When facing a 90-degree bank turn with slow speed and low altitude, you do not have a few seconds to spare. During these few seconds, the airspeed continued to bleed off, exacerbating the already precarious stall situation. Keep in mind, that during a stall, airflow starts to separate from the airfoil further forward on the wing. So despite the attempt to recover, there was insufficient airflow over the right wing to allow the fully deflected spoiler to recover the aircraft. And having a spoiler ("lift-killer") on a stalling wing, instead of an aileron, didn't help the situation.

Now let me turn to one of your questions...why did bank angle continue to increase? It's impossible to tell exactly when the pilot attempted to stop rolling. So trying to tie an increased roll rate/bank angle to an aerodynamic explanation in this case is futile. What is known is that the aircraft commander on that fatal flight had a documented history of pushing the rules, abusing limits, and ignoring authority. The end-game of this accident may have been exacerbated by the existing aerodynamics, but the accident was caused by one person's selfish thrill-seeking at the expense of his own life and three others, and the loss of a multi-million dollar aircraft.
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Old 10-06-2010, 10:31 AM
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Nice reply, Wollac- you must be a BUFF pilot. There are several on these forums, so hopefully another can add a more using what they know about the B-52. Hindsight2020 is another one, he has a strong background in aeronautical science. Reasoned speculation is the limit without introducing CFD analysis or some other high-tech methodogoly. Generally what happens with these investigations is a team makes a model of the aircraft, applies blackbox data set to what the plane did near or at the time of the crash, and then use a fancy simulator to determine a plausible chain of events. You can use a desktop sim like X-Plane to do some of these calculations. That is what I do although the simulation is heavily simplifed by the limitations on my computing power and the simplicity of the model. So it is not much better than flying a toy model for the most part, but at least it shows what a simplified airplane would do.

What is your preliminary plan of attack? If you wanted some food for thought, you could study the NASA wind tunnel videos of similar wings available on YouTube. I would examine the oil streaks at lower q's and higher AoA's to geta rough idea of what happens in a 1-g stall. The same aerodynamic behavior should extend to higher gs. The music is a bit out of date (kidding).

NASA video 1 (YouTube)

NASA video 2 (YouTube)

NASA video 3 (YouTube)
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Old 10-06-2010, 09:31 PM
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Originally Posted by Wollac View Post
... Also keep in mind, that it takes the B-52 hydraulics several seconds to go from full spoiler deflection on one side to full spoiler deflection on the other side....
Not true. Full deflection is almost immediate when normal aircraft hydraulics are powering the spoilers.

You're probably thinking of the airbrake, spoiler and lateral trim checklist step on the ground which only uses the ground test pumps and wing standby pumps to power the spoilers/airbrakes.

OP, the best source of B-52 flight characteristics is Chapter 6 of the Dash 1 (the Buff flight manual).

Also, a Google search on "Czar 52" will provide ample sources of the information and flight characteristics you're looking for.

Last edited by nfnsquared; 10-06-2010 at 10:38 PM.
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Old 10-07-2010, 08:59 AM
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Something tells me the investigation will contain all that. I don't think you're going to find any rocks left to kick over.
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Old 10-07-2010, 09:12 AM
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If you get a good copy of the video, you can see once the nose is below the horizon, it is essentially over. You can also see that almost all the way to impact, the spoilers on the right wing are fully up. What can not be seen is rudder deflection. As anyone can see, the vertical fin and rudder are the largest flight controls. And without a leg of rudder, spoiler alone is probably not sufficient at low speed to roll the BUFF out at slow speed and bank angles near 90deg.

You probably know the BUF has two flap settings.. UP and DOWN. No intermediate settings like on Boeing's other machines (707, 727, 737, etc). You probably also know Holland was well known for pushing the BUFF up to and often near the limits. And that because of his rogue flights, the Ops officer had decreed that he was the only one to fly with Holland.

One has to wonder if a -52D (with ailerons) would have been able to recover. From the video it looks like Holland put the airplane in a situation low speed, low altitude, nose low and it was not recoverable.

FWIW, I have read that the BUFF went in very NEAR the nuke dump. Don't know if that was true.

Also, my experience with the BUFF comes from one sortie in the H and many sorties refueling them as well as reading a lot about Holland, the event itself and the aftermath. I may be wrong.
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Old 10-07-2010, 02:06 PM
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I believe if you watch the video, the aircraft was at a high AOB as it pulled closed. After completing roughly 180 degrees of turn, the AOB increases which then leads to the aircraft stalling.
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Old 10-07-2010, 08:27 PM
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Originally Posted by inter09 View Post
I'm struggling to support this, using the aircrafts aerodynamics, how it uses spoiler deflection to roll, its swept wings, adverse yaw, sideslip, overbanking, why bank angle continued to increase, roll rate. any help is much appreciated.
I think that's the key. Had he leveled the wings, none of those other factors would have mattered. But at 90 degrees of bank, the absence of any of those factors would not have saved him, either.

It's interesting that in his initial turn away from the runway heading, the aircraft attained a bank angle of about 60 degrees, shallowed to about 45, then rolled back to about 90 degrees of bank at the time of impact. From this it would appear that the airplane at that weight and configuration is controllable through at least 60 degrees of bank, and that the flight controls were operating normally.

From an "aerodynamic perspective" what happened to Czar 52 is pretty evident...the aircraft overbanked, causing the nose to drop at an altitude too low to permit recovery. Why it happened cannot be determined without access to aerodynamic data or test pilot reports pertaining to that particular model of B-52, although I suspect that he was trying to avoid the embarrassment of turning what should have been a simple "360" into a "Figure J" maneuver over his home airfield.
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Old 10-08-2010, 05:22 AM
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It is believed that CZAR52 increased bank as to not fly over the restricted area. So halfway during the turn, the pilot increased bank and simply stalled the aircraft.

Here is a picture I found from wiki who also reports the same findings. I'm not sure what the actual final USAF report found. However, I believe it was strictly pilot error and not an aerodynamic problem with the buff.



For most aicraft pulling closed, the turn radius would have taken them outside the restricted area, and would not have been a factor.
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