Aviation News

May 1, 2013

National Air Flight 102: A Preliminary Report

More articles by »
By: NYCAviation Staff
Tags: , , ,
Multiple MRAP vehicles strapped inside of a 747-400 in a similar way to that of the National Air 102 crash.
Multiple MRAP vehicles strapped inside of a 747-400 in a similar way to that of the National Air 102 crash.
EDITOR’S NOTE: The following is an independent analysis and is in no way an official investigation.

FACTS FROM VIDEO

- Aircraft had a very low forward airspeed during the stall and on impact.

- The landing gear was down.

- Engines emit smoke just before the stall.

- Flaps were in a takeoff position.

- There were vapor trails from the wing tips. horizontal stabilizer, and engine pylons as the aircraft lost altitude.

- Engines shoot forward on impact approximately 200 feet.

- Left wing dips at the beginning of the stall, followed by a rotation to the right that ends when the bank angle approaches 90 degrees.

- The fire indicates there was a light right headwind/crosswind.

ANALYSIS

Informal analysis: (based on observations, assumptions, and deductions). Note, investigators will be reviewing all evidence, and the conclusions will be more soundly reasoned than this analysis based solely on the video footage.

The fact that the gear was down indicates that the crew was experiencing problems immediately after takeoff that focused their attention elsewhere. From the video, you can see the aircraft’s speed was deteriorating. There is a transient smoke stream from the engines just before the stall, which is an indication of an acceleration of the engine core’s RPM – the crew were likely firewalling the throttles. There was a light dip of the left wing at the beginning of the stall. The pilot likely countered with right rudder, a correct but excessive input that caused the aircraft to enter a spin to the right. At this point, airspeed appears to be nearly undetectable but probably around 100 knots.

Swept wing aircraft, especially ones with high angles of sweep like the 747, pitch up at the last moment of a stall before the nose drops and airspeed is recovered. In the video, the nose does not drop until the aircraft is on its side and rapidly loosing altitude. Once the aircraft is on a knife-edge, the airflow will cause the vertical stabilizer to weathervane. This brings the nose down. During this time, the right rotation also stops. If there had been an engine failure, the rotation would have continued in the direction of the failed engine. As the wings are brought level, the nose down attitude remains stable through impact. At this point, there are vapor trails from the horizontal stabilizers and wing. This indicates a high pressure differential which is clearly from the high angles of attack on the surfaces.

The crew had a controllability problem that was present from rotation. Pilot training and instinct is to lower the nose if the aircraft is pitching up. This wasn’t possible. To put this aircraft in the position it was would have required excessive nose up elevator or excessive rear Center of Gravity (CG). Since this was a routine flight and the aircraft had not likely had major maintenance causing a critical failure of the flight controls, a rear CG is the likely problem.

This is also indicated on the final moments prior to impact. Had the CG been in the proper location, the nose down pitch would have continued as the CG forward of the wing’s lift would have accelerated towards the earth from gravity while the wing resisted this acceleration due to airflow (drag) on the wing, even with a major failure of the trim or elevator. Just prior to impact, the pitch remains mostly stable, indicating the CG was between the wing and tail, and the weight on each was proportional to the lift being generated. The proportion of the surface area of the wing to tail surface would be equal and inversely proportion of the CG between them. Ie, if the surface area was 70% wing and 30% tail, the CG would be 30% back from the wing, or 70% forward of the tail.

There are many other possibilities, example pilot error. Though this is unlikely, these must be considered until conclusively found otherwise.


  • hidflect

    Amazing how much can be clarified with a simple bit of video footage.

  • http://www.facebook.com/people/Mike-Crognale/1609747611 Mike Crognale

    Looked to me like the cargo broke free and moved aft as she rotated and lifted off. Dead men from that point on.

  • http://twitter.com/EMDiii Edward Doyle

    Another point to ponder is that that the accident aircraft was a converted passenger airplane. The MRAP does not look like it fits under what was the upper deck of the passenger compartment thereby requiring that the load be over and aft of the wings. This configuration/load would most likely require more cargo up front or ballast fuel. I don’t think this would be an ideal loading situation but time and a thorough will answer what really happened.

    RIP to the crew.

  • Ed Bolduc

    This video ripped my guts out. Very hard to watch, especially when I know that place very well.

    Not sure if the 747-400 will allow the engines to overspeed (not type rated on this A/C so cannot say). However other “newer” aircraft engine controls are controlled by an auto-throttle that allow maximum engine performance for current conditions. Some aircraft have an “Override” for this, and if the -400 does then I’m sure they were bending the throttles trying to get everything out of those engines (and thus probably some carbon burning off as smoke)

    That being said Boeing airplanes typically allow the pilot to have the final say. This is a major difference from Airbus who gives the computers the final say in performance. Even the 777 (Fly-by-wire) will allow a pilot to stall the plane, where as Airbus equipment only allows FBS “Full back stick” to a maximum AoA. There is a famous video of the Airbus 320 flying right into the tops of trees because the airplane thought is was time to land but the pilot was trying to climb. There were some training issues as well that I’m sure have been resolved. However no design is “human proof” as we prove over and over again.

    It would seem a load shift is likely, however this link seems to say otherwise (apply grain of salt here).

    http://www.sacbee.com/2013/05/01/5387895/statement-from-national-air-cargo.html

    The plane only stopped for gas, no pax or cargo on/off load. So it might be interesting to find out what the investigators come up with.

    Sometimes these can be called “milk-runs” but I have a saying, “Murphy loves to ride Space-A” Anything can happen, straps and devices can break, someone could have released a lock accidentally, shit happens when humans are in the mix.

    Landing gear being down does say they were busy. But with the AoA as it was, I would imagine the airplane was full of bells and warnings and Betty saying “STALL…STALL…STALL….” Followed by “TERRAIN..WHOOP WHOOP PULL UP” That’s gonna be the last thing on the recording…maybe a lot of swear words as they were trying to arrest the situation.

    Also heard reports of the crew calling the tower declaring their emergency. However, some reports said the crew called and said they had a load shift. I can tell you if I have my hands full of 500K+ of airplane pointed 50 degrees + into the sky in Afghanistan (where performance already stinks) that the LAST thing I want to do is talk on the radio. Especially when more than likely the reply would be “Say Again?” So I don’t have much faith in those reports until the NTSB says it happened.

    Engines moving forward at the impact simply means they were working. A dead engine would not have continued forward but would have stayed with the wing. When the NTSB report is released operating engines will be indicated by deformation of the compressor and turbine blades. These will typically “warp” at impact.

    Of course the FDR and CVR are more than likely give many clues. Since this accident isn’t much in the mainstream news, and due to it’s remote location (away from proper analysis facilities) I’m not sure how long it will take until/when/if they release the CVR recordings.

    Agreed that the pilots knew something was wrong, perhaps prior to it if the were past refusal speed, and elected to take the airplane flying vs run off the end of the runway.

    Pretty sure the runaway trim/stab EP is practiced by everyone from the time you first have electric trim until you are a Captain in a Major. It sucks, but if you react quickly enough (and you know real quick when it happens) you can still fly it, you just sweat a lot more.

    A broken stab on the other hand…..

    Again, not a 747 guy, not sure of the company SOPs, just throwing $.02 in.

    RIP

  • Jerome Dawson

    Goody synopsis. One nitpick, though (sorry, it’s the tech writer in me): it’s “losing” altitude, not “loosing”. Otherwise, please keep up the good work!

  • Jerome Dawson

    And then I have “goody” in my post. Sheesh!

  • http://twitter.com/China_Marine ChinaMarine

    They’re only using basic cargo tie straps…? For a 15 ton vehicle..? Wow… I would have guessed they would be using standard, Military spec tie down chains, 2 or 3 standard tie down chains could probably hold that MRAP up inverted… They have a tensile strength like you wouldn’t believe… I am also wondering if any members of the crew were prior military… Anyone know..?

    • http://www.facebook.com/azrael.bloodlust Bloodlust Azrael

      Those straps are probably rated at 6klbs each.
      When your loading aircraft. Weight becomes fuel. you use straps, not chains if possible.

    • http://twitter.com/China_Marine ChinaMarine

      They don’t weight that much, and they are widely used throughout the Military and nearly every aircraft capable of carry cargo… Talking from Experience… And 3 of those chains probable equal 50 of your tie straps, NO Comparison in strength.. It’s Standard SOP to use these, when dealing with Heavy Items like were used in this case. Have your ducks in a row, before you speak.

    • Guest

      I agree. I was on C-17s out of KCHS for 10 years, and on 17s, we never tied down heavy equipment with straps. We always used chains and devices and you NEVER mix chains and straps. The reasons being are: 1.) obviously you use less pieces, 2.) there’s no stretch to chains and devices, where there is stretch with straps and 3.) you have more strength on the effective length and angles and not just on the actual lengths. On this load it would take only one of those vehicles to get loose and hit the next back, and then it’s just a domino effect from then on.

    • Chris Tex Fowler

      I agree. I was on C-17s out of KCHS for 10 years, and on 17s, we never tied down heavy equipment with straps. We ALWAYS used chains and devices and you NEVER mix chains and straps. The reasons being are: 1.) obviously you use less pieces, 2.) there’s no stretch to chains and devices, there is with straps, and 3.) you have more strength on the effective length and angles of chains and not just on the actual lengths. On this load it would take only one of those vehicles to get loose and hit the next back, and then it’s just a domino effect from then on. If that is [in deed] what happened, the chances of that happening would have been far less had they used chains.

    • Marcel

      I am a B747 loadmaster and chains are only used from the cargo to the pallet. There is no way to attach a chain to the maindeck floor of the aircraft.

  • http://www.facebook.com/azrael.bloodlust Bloodlust Azrael

    How much trust can we put in a paper that misspells “Losing” as Loosing.

  • jem777

    These are absolutely heavy flight with huge cargos. http://paradisecopters.com/