Cyprus-Forum.com

[Kikapu]

We have had slew of Plane Crashes in the last couple of months, so perhaps we should have a thread on the subject to all those who have interest in aviation to discuss these accidents. We have discussed the resent Turkish Airlines crash extensively and now perhaps we can move to other recent crashes, including the two yesterday, one FedEx in Tokyo and another in Montana, both crashes killing all aboard. I'll give you my take on the cause of the FedEx crash soon, and having seen the footage on it, it appears strong winds played a major part in that crash. I'll try to explain on how the strong winds caused that crash. Others can add theirs also.!

[Oracle]

Maybe Gravity is getting stronger ....

.... Mmmm ... Wonder what's happened with the Large Hadron Collider recently .....

[Oracle]

Quick check:

Nothing much! ... Just some faulty magnet .....

[Kikapu]

Maybe Gravity is getting stronger ....

.... Mmmm ... Wonder what's happened with the Large Hadron Collider recently .....

Still out of action as we speak. I saw my friend recently who works on it, so rest assured, that gravity has not been altered, nor has there been any "black holes" created.!

[Oracle]

Poor gullible, naive, trusting little Kikapu ....

The spinning protons are increasing the magnetic forces ... I can feel it!

[DT.]

Poor gullible, naive, trusting little Kikapu ....

The spinning protons are increasing the magnetic forces ... I can feel it!

You sure its not the smell of the kanaourkes out in paphos fields you're experiencing Mrs O?

[Kikapu]

If you study the footage above on the FedEx MD-11 aircraft, it appears to have made a good initial landing on its main landing gear before everything going deadly wrong thereafter. So what could have happened that made the aircraft bounce couple of times on the runway before going out of control completely and ending up doing a "cartwheel" with the left wing smashing against the ground.?

It was reported that there were gusts of wind up to 74 km/hr or 45 mph. Planes landing into the wind is always a benefit, as it reduces the "speed made over the ground" when approaching landing, even though the plane is still flying at it's normal speed through the air. For example, lets say that the FedEx plane was approaching to land at 160mph, but the head winds is at 45mph, which makes speed made good over the ground at 115mph, which is an advantage coming in for landing, as it appears that the plane is travelling slower than it actually is, to make the landing. The only problem with such high head winds however is, that the moment the planes main landing gear makes contact with the ground, the airflow speed over the wings will instantly become 45mph more than the speed the plane was already travelling at, which was 160mph. So, the moment the plane touches down, the airspeed over the wings just became 205mph, which is way more than what the plane would have needed for take off even with a maximum load. I believe it was this high speed of airflow over the wings that made the plane take off again (bounce off) after the initial landing, since specially the flaps for landing would have been at extended at max to produce lift at low speed, as well as having the "ground effect" play part with the air between the wings and the ground.

Once the plane became airborne again, it instantaneously lost the 45mph wind force over it's wings, so it was back to 160 mph minus what ever speed the aircraft lost in the meantime as it was landing. The aircraft now is either very close at stalling speed or has already reached stalling speed. Then the aircraft makes another bounce, but harder one this time, and again, the 45mph wind once again flows over the wings of the aircraft, which once again, produces lift which would have been more than what it needs for take off along with the aircraft landing speed. So the aircraft tries to take off one more time, since the pilots are no longer in control of the aircraft anymore in trying to deploy the "air brakes" on top of the wings, or the "reverse thrusters" with the engines to reduce speed and lift, as it is done after each landing. After the second bounce, the aircraft is now totally in stalled speed and is in a free fall and out of control travelling at high speed, which resulted in the left wing hitting the ground and cart-wheeling down the runway.

We don't know how much cargo the plane was carrying. It is possible, that it had very little cargo, which the plane would have been relatively very light in comparison to a MD-11 with an airliner. Therefore, the added 45mph head wind would have played a major factor upon the plane landing which would have caused the aircraft to take off immediately, because the pilots would not have had enough time to deploy the "air brakes" and the "reverse thrusters" yet. These cargo planes are nothing but a long tube when empty, and extremely light. I once flew with a completely empty FedEx Boeing 747 in the "jump seat" from Los Angeles to Oakland, California, and it was amazing just how quickly the plane took off. I don't think we even used a mile of runway. Full power and empty shell of a plane, we were up in the air in no time at all, followed by with a steep climb.!

I'm very sorry for the lost of the FedEx crew on this crash, but once the aircraft started bouncing on the runway after the initial landing, it was out of their hands on what the outcome was to become. Gravity and aerodynamics of High/Low air pressures on the wings were in control once the pilots were no longer able to command the aircraft. Perhaps others can point out if I gotten this theory wrong, like BigOz, Skyvet or Paphitis.!

[Kikapu]

Paphitis,

Can you give us your understanding as to what happened to FedEx MD-11 crash. I gave my best understanding as to what may have happened that caused the crash (see above), but would love to hear yours also since others interested in aviation have kept away. Thanks.!

[Paphitis]

Hi Kikapu,

I am not at all familiar with this aircraft but it is important to understand that every aircraft has its peculiarities.

The MD-11 has a rather substantial design flaw in that the aircraft has a significantly reduced tailplane. As a result, a Longitudinal Stability Augmentation System (LSAS) was fitted to assist with Pitch control. The consequences for LSAS failure on this aircraft could have caused this accident as the aircraft would not have enough elevator trim to execute a missed approach or Go Around procedure, especially if the aircraft had an aft Centre of Gravity (CoG) at the time. This aircraft also has a history of tailstrike, which means that the pilots may have pushed the nose down after the initial bounce, thus causing Pilot Induced Oscillation (PIO) which is the tendency to apply rapid over corrections in elevator control inputs in the opposite direction (pushing the nose down) after bouncing in order to raise the tail and avoid a possible tailstrike scenario, thus resulting in hitting the ground very hard on the nose wheel.

I am not aware if there was any cargo on board. If the aircraft was completely empty, then the aircraft could very well have an aft CoG but within limits. This too could be a contributing factor. If there was cargo on board then we should also be open to the possibility of cargo shift aft resulting in the CoG moving aft outside of design limitations. As the aircraft is also arriving at its destination it would have also a minimum amount of fuel on board. It basically would only be carrying Fixed and Variable Reserve fuel as all the Flight Fuel (FF) would have been burned thus causing the CoG to also move aft, although pilots must always ensure that the aircraft is balanced throughout the whole flight by entering the data on the Load and Trim Sheet, but add Cargo Shift into the fold, then you have a tail heavy aircraft. Cargo must always be properly restrained but Cargo Shift has occurred in the past.

The following is from the MD-11 Flight Manual:

Bounced Landing Recovery

If the aircraft should bounce, hold or re-establish a normal landing attitude
and add thrust as necessary to control the rate of descent. Avoid rapid
pitch rates in establishing a normal landing attitude.

CAUTION: Tail strikes or nosewheel structural damage can
occur if large forward or aft control column movements
are made prior to touchdown.
When a bounced landing occurs, consider initiating a go-around by use of
normal go-around procedures. Do not retract the landing gear until a
positive rate of climb is established because a second touchdown may
occur during the go-around.

Another contributory factor would also have to be the strong winds. When I go back to work, I will print the aerodrome layout and I am still trying to find the Aerodrome MET Report (METAR) of the actual conditions at the time of the accident. This is important as I would then be able to work out what the Cross Wind (XW) and Head Wind components were on impact. Wind Gusts could also likely be a contributor, because so often in strong wind situations (74kts), the wind is not always constant but is gusting, and we all know that Lift is directly proportional with Airspeed over the wing. A strong crosswind could have also contributed to the inadvertent roll as Lift is always greater on the side the wind is blowing from if this is not counteracted.

It is important to also understand that all of this is largely guesswork or speculation. Aircraft Investigation is very complex and intense and I am only a pilot who has not flown this type.

Kikapu, I am just shy of 9,500 flight hours. The first aircraft I ever flown was a Piper Warrior and Piper Arrow Aircraft. I was then trained on Pilatus PC-9, Machi MB-326 before being assigned to the AP-3C Orion. I now fly De Havilland Dash 8-202/315 aircraft. Most of my experience was on Orion aircraft. So I know very little about the MD-11.

This accident is very much an eye opener for all pilots. It just goes to show how quickly things can turn real ugly. In all my flying experience I too have managed to bounce an aircraft along the runway many times. I have also had atrociously hard landings, but these days it does not take much for me to conduct a missed approach.

[Raymanoff]

Why waste time here talking about it when you can get all the info here: http://www.airdisaster.com/