Part 3 of 5:
Originally Posted by p51guy
The Air Florida crash was caused because the engine anti ice was not turned on and the epr probes gave eroneous readings. If they had just advanced the power beyond the max epr they would not have crashed. The epr reading was wrong because engine anti ice was turned off. Florida guys are not that familiar with icing conditions. I for one. They made a terrible mistake that morning. I felt it in my gut when they crashed because I was flying a 737 also in California and knew something went wrong. The heroes that jumped in to save the passengers are still in my mind. I agree with pushing the thrust levers to the limit when things go south. Years ago during Air Florida times they didn't have thrust limiters but they do now. The computer would have probably not given them the power they needed today either if the engine anti ice was turned off.
Originally Posted by punkalouver
I should think that if the Air Florida guys had not taken off with a bunch of wet snow on the wings, they would not have had their pitch-up. If they had bothered to turn the engine anti-ice on, they would have had their proper power setting for takeoff and there would not have been a need to add a bunch of thrust just to get to takeoff thrust. Somehow, I think they would have been in a better position if a normal thrust setting was used for takeoff. Doing a powerback from the gate on a heavy snow day in a 737 seems to be a strange decision as well.
A couple of comments here …
The critical mistake that was made was not made by the company or the flight crew. The critical mistake was improperly deicing/anti-icing the airplane (more later). There is no indication that the crew elected to attempt a takeoff with “a bunch of wet snow on the wings.” That certainly was the allegation made … but what was the reasoning behind that allegation?
This position was generated primarily from the interview of, and a picture taken by, a passenger on board an aircraft taxiing past the accident B-737 when it was still at the departure gate. The records of that particular flight (i.e., “block-in” time) would strongly suggest that the photo was taken just minutes prior to the accident airplane pushing back. While the black and white copy of the photo is accurate, it doesn’t do the justice to the scene content that the original color photo does; and FYI, the black and white version can be seen in the Accident Report copy. The photo clearly shows the B-737 with significant snow and ice all over the airplane. Conclusion … the flight crew departed with all that snow and ice covering the airplane.
Support for that position (if one is inclined to need it) can be “read into” some of the comments made by the flight crew on the CVR. For example, the F/O statement, “…this one’s got a quarter to half an inch on it all the way.” However, this comment simply cannot be referencing
his aircraft. From the cockpit it is impossible to see the wing “all the way.” In fact, only the wing tip and about 6 feet inboard from that point would have been able to be seen from the cockpit. Recall as well, the visibility was quite poor – down to 1500 – 1800 RVR, and it was snowing. The light level was more likely equivalent to dusk than mid-day under a clear-sky. The distance from the cockpit window to the wing tip is something on the order of 65 – 70 feet. Someone would have to believe that the F/O could see ¼ inch of ice under those conditions. Additionally, the statement made by the F/O immediately following clearly shows that his comment is directed toward the airplane they are following (“Look how the ice is just hanging on his, ah, back, back there, see that?”). Besides, the purpose of the deicing/anti-icing procedure is to eliminate all snow or ice that may have been adhering to the aircraft, and the crew was likely of the understanding (now, understood to be untrue in all cases – but not then) that any falling snow would have fallen on a “protected” wing or fallen on a wing that had been cleaned, and then dried … allowing any snow to have been swept off the wing during the first portion of the acceleration – as was the understood and accepted practice at the time.
But, I digress … back to the photograph “evidence.” The photograph
clearly shows a line of baggage carts parked in front of the right wing, with the forward cargo door clearly open. Testimony of the baggage loaders, those who actually conducted the deicing/anti-icing process, those that pushed the aircraft, and the gate personnel verify that no baggage was loaded on the airplane at any time after the deicing/anti-icing had been completed. It isn’t rocket science to understand that the snow and ice on the airplane seen in the photograph was not on the aircraft after the deicing/anti-icing process. Therefore, the flight did not taxi out with the snow/ice on the airplane that is indicated in the photograph. They taxied out after being deiced/anti-iced in accordance with what they thought was proper procedures.
Regarding the allegation that “
Doing a powerback from the gate on a heavy snow day in a 737 seems to be a strange decision as well” … The crew did
not “powerback” from the gate. Initially, after starting engines at the gate, the tug originally used was slipping on the ramp and was unable to push the airplane (more about that below…). As a result, the Capt elected to open the thrust reversers to negate the residual forward thrust on engines at idle in the hope (apparently) that the tug would then be able to successfully push the airplane. It was not successful. The engines were shut down and a much larger tug was brought in to do the push. Engines were started on the ramp after being pushed back.
Regarding the allegation that “
…if the Air Florida guys had not taken off with a bunch of wet snow on the wings, they would not have had their pitch-up.” … The pitch up was, indeed, due to ice accumulation on the wings – not the wing lifting surface as much as on the leading edge of the wing … and it did not come from the snow/ice as seen in the photographic evidence (as described above) and it did not come from the falling snow during the taxi out operation. The aircraft immediately in front of the B-737 (“Apple fifty-eight”) and the aircraft immediately following the B-737 (“six eight gulf”) both took off successfully – after being exposed to the identical inclement conditions. Where did the ice come from then?
The accident airplane was deiced before push-back. However, as indicated in the NTSB report, there was an earlier malfunction in the de-icing truck and the ground crew made improper repairs. This resulted in drawing only from the water tank when the volume of the spray was anything above the “ON” position dribble out of the nozzle. When the water/glycol mix was determined at the mix station, the mixture at the hose-end
was correct; but, and its worth saying again … whenever
any increase in volume flow was needed (by pulling harder on the “trigger”)
ALL of the increase in fluid came from the water tank –
NONE came from the glycol tank. Essentially the airplane was deiced with hot water. Subsequently, when a top coating of 30% glycol
would have been evenly sprayed over the entire airplane – it was sprayed with water … which promptly froze in the 22-degree weather. The crew believed they had no ice on the airplane. Not very many airplanes are deiced with water – carefully, all over the airplane, with particular attention given to the lifting surfaces, when its way below freezing outside. The fact that the deicing/anti-icing process was carried out essentially with water, it is little wonder that when a tug attempted to push the airplane back, it was slipping on the ice that had accumulated on the ramp … after the ramp was sprayed with water. Should we be surprised in that?
If you will allow me, I’d like to look at simple, straightforward aerodynamics, and what role those aerodynamics played in what happened. We know that during the initial portion of any acceleration for takeoff, the wing is beginning to develop lift. But it is not until the pilot rotates the airplane, getting the wing to an AoA that generates enough lift that the airplane gets into the air. I’m sure that it isn’t any super revelation to state that the wing does not generate lift uniformly and the entire wing doesn’t generate lift simultaneously. You and I know that you can get an airplane into the air, in ground effect, before it is really ready to fly outside of ground effect. We know that Vmu tests are done where the controls are essentially held back from early in the acceleration run, forcing the tail onto the ground (or very close to it) at a speed well below what is necessary to fly – to see what the minimum lift off speed will be. The reason pilots don’t rotate the airplane prior to reaching “rotate speed” is that they don’t want the airplane getting into the air until the wings support the airplane properly and controllably. This is what they learn. This is what they expect.
But, what would happen if we changed the equation a bit – right at that critical moment – when the pilot moves the control column to a “neutral position, or slightly aft of the neutral position, in preparation to rotate” (a quote from the Boeing manual). What if, at that moment, the pilot realized that pulling further back on the controls would not get the airplane rotated? The pilot, pulling like crazy on the controls, gets no rotation. I know that Air Force KC-135 instructors and evaluators are (or, at least were) trained on the unique use of the spoiler panels. Under the glare shield were 2 guarded switches that controlled 2 valves to open (or shut off) hydraulic pressure to either the inboard spoilers (L) or the outboard spoilers (R) on each wing. In this case (no rotation – and you had to know that the KC-135 had p*ss poor brakes and no reverse thrust – quick stops were not made with any regularity) and you wanted to get into the air, you would turn off the inboard spoilers, grab the speed brake lever, and gradually, very gradually, raise the speed brakes. With the inboard panels shut off, the only spoiler panels being raised were the outboard panels, creating differential lift – lift on the inboard portion (forward) and no lift on the outboard portion (aft). The airplane would rotate just like “normal” and when you got the pitch attitude you needed, you lowered the speed brakes, just as gradually. If you yanked the spoiler handle up quickly, you would very likely smack the tail on the ground. Differential lift at takeoff can be very interesting, to say the least.
In the accident B-737 situation, a very similar circumstance was handed to an unsuspecting crew. Recall the F/O had indicated that he intended to just get the nose gear into the air and then let the airplane "fly off the runway." Is that what happened? No, it wasn’t. When the F/O moved the control column to the neutral position, the inboard portion of the wing was generating lift – and the outboard portion was not. Presto. Rotation. Very quick rotation. All the way into the stall buffet. In approximately 2 seconds. Normal rotation rate is 3 degrees per second. Stall buffet is beyond "stick shaker," and estimates were that to get the buffet the pitch attitude would have to be approximately 24 degrees - that would require a 12-degree per second rotation rate. Does that sound like getting the nose gear into the air and then just letting the airplane fly off the runway, as the F/O indicated he was going to do? Once rotated and airborne, the crew couldn’t get rid of the differential lift. They couldn’t get the nose down. Straightforward aerodynamics. The only thing they could have done was to run the horizontal stabilizer to a more nose down position, and that
may have allowed them to lower the nose;
maybe. Or, they could have attempted to roll the airplane to help get the nose down. But the portion of the wing in front of the ailerons was aerodynamically crippled.
Regarding the allegation that “
… there would not have been a need to add a bunch of thrust just to get to takeoff thrust. Somehow, I think they would have been in a better position if a normal thrust setting was used for takeoff” … if the airplane had been kept on the ground long enough to accelerate to a speed that would have allowed the outboard portion of the wing to generate enough lift to counter act the rotational moment, they probably would have recognized a “sluggish” airplane – with only 75% power. But they didn’t know to do that. They wouldn’t have been able to do that – even if they had shoved the throttles to the firewall at brake release. They had always planned to rotate at the computed speed. They got ready to rotate at the computed speed. They expected the airplane to fly at the computed speed. What they didn’t expect was a wing deiced with water; a wing that now had a thin coating of ice that deformed the leading edges; deformed just enough to cause this very unique aerodynamic problem – from which they were incapable of recovering.
Additionally, as I indicated earlier, the F/O had been an F-15 ADC pilot operating out of Minot, North Dakota. It probably won't surprise many that most people recognize that it
does snow in Minot, North Dakota.