Mission Impossible

EVERY ONCE IN AWHILE something goes so badly wrong in an aircraft that not even the designers or manufacturers considered it plausible.

When it happens in a jet fighter you cut your losses, curse your luck and escape on the ejection seat. In an airliner, you stay in the game, play your best cards – and stretch your wits to the limit!

Here’s the scenario – you’re the captain on a long haul flight over the ocean in a modern twin-jet airliner. You notice a fuel imbalance developing between the fuel tanks. You read the checklists and take the appropriate action, but what you fail to recognize is that the imbalance is caused by a fuel leak on an engine pylon! In due course both engines flame-out from fuel starvation, and you’re now the commander of the world’s biggest glider.

Unrealistic simulator exercise? No, not really. It’s happened several times, and always for different reasons. Remember the Boeing 767 in Winnipeg – landing on a drag strip? More recently the Airbus A330 over the Atlantic at night, deadsticking onto Terceira Island in the Azores? Both these events were successful gliding attempts, miraculously resulting in no loss of life and substantially little damage to the aircraft. Another, a DC8 in the seventies, wasn’t so lucky. All aboard were killed. I know that the captain on the 767 had gliding experience – I’m not sure about the other two. Skill or luck? Probably a healthy dose of both.

Some emergencies are just so improbable that very little attention is paid to training for them; while others are of such a freak nature no one would have even thought them possible until they actually happened!

Recognizing this, one of the informal exercises SAA gives in the 737 simulator, is a dual engine flameout from overhead the airfield at ten thousand feet. Naturally the aircraft doesn’t perform like a glider – but she doesn’t fall out of the sky either. In fact, relatively speaking, the 737 glides rather well – until you start hanging the gear and the flaps out. After that, things start getting a little hairy. The enormous drag from these components means you need to be at least twice the height over the outer marker as you would on a normal approach. Basically the same descent profile as the Space Shuttle.

Another exercise given in the simulator is “Advanced Manoeuvre Training.” This was recommended by the FAA to all 737 operators after several incidences in the US of “rudder hardover.” Essentially what occurred was an uncommanded deflection of the rudder during flight, resulting in the aircraft suddenly yawing, then rolling over and entering an inverted highspeed dive. The condition is recoverable provided corrective action is taken almost immediately. This would come as second nature to anyone with even the most elementary of aerobatic training. But as most civilian pilots have no form of this training the FAA felt it necessary to advise operators to formulate some kind of unusual attitude recovery program in their simulators to prevent an unwelcome rush of adrenaline, or worse, a premature visit to the undertaker. SAA’s program was designed a few years ago by Captain Tony Van Vliet and has proved not only beneficial but also extremely enlightening. One finishes the session amazed, not only at what the 737 can do – but also at what you can do!

A more unusual exercise, not normally trained for, is a replay of the United Airlines DC 10 accident in Sioux City in 1989. Whilst cruising along at FL350 the tail mounted engine disintegrated. Not too life threatening on its own – but to give the event a really challenging twist, it blew out the hydraulic actuators to the flying controls in the process. Suddenly the crew was faced with the mother of all tasks in getting this behemoth back on the ground. No elevator, rudder or aileron control! And to crown it all, no trim, gear, flap or speed brake either! In fact, so remote was the chance of these failures occurring simultaneously that no exercise of this nature had ever been contemplated for training – not even in a flight simulator! And to stack the odds against them – the crew would get only one shot at it! No rehearsal and no second try. A low level go-around in that condition is not possible, for reasons that will shortly become evident.

I’d forgotten about this incident altogether and it was only when it was dramatized in the TV documentary “Black Box” a few years ago that I thought I’d recreate first hand what the crew were up against.

And so it was that late one night after my 737 students had gone home, I decided to go back into the simulator and ‘ restage their experience. I must say here, that it is without doubt the most harrowing exercise imaginable! The exact circumstances cannot be accurately replicated in a 737 because of a manual reversion system for the flight controls that the DC 10 did not have the benefit of. (Hence the reason we do not train for it.)

To recreate the exact situation facing them, you have to deny yourself the use of any flying controls whatsoever! Feet on the floor and stick hand on the knee! You have control of the thrust levers alone and nothing more! Mission impossible! Here’s where you go back to basics. Remember the pitching effect of thrust? Well, on a swept wing jet with the engines underslung below the wings, the result is more pronounced.

And that, fundamentally, is how they did it! With the remaining engines being on the wings, applying thrust pitched the nose up into a climb and the opposite occurred when throttling back. Turning the aircraft was a little easier. Application of judicious asymmetric thrust results in an amazingly accurate turn. Getting the wheels down is accomplished with the emergency gear extension. No hassle there – but getting the leading and trailing edge flaps out proved to be more problematic – and here a very serious complication crept in. Remember the effect of trim? Undisturbed an aircraft will attempt to maintain its last trimmed indicated airspeed. Same principal applies in a jet. So what, you say! Well, the last trimmed speed in the cruise before the engine exploded was around 250 knots IAS! (450 knots TAS.) Without sufficient drag and lift from the flaps, the aircraft’s trimmed speed remained impossibly high for an approach and landing! This is where things become very arduous indeed. In the aircraft’s attempt to maintain its last trimmed speed, any change in thrust causes a sluggish porpoising motion know as a phugoid. (Try it next time you’re in the cruise with lots of height. Trim your aircraft for a speed then let go the controls and change power. Notice how the aircraft’s pitch oscillates to follow the ‘ speed. DO NOT TRY THIS NEAR THE GROUND!)

Left alone and undisturbed, the phugoid stabilizes together with the speed, but with the thrust/pitch change corrections essential for a survivable sink rate it becomes virtually uncontrollable! The trick here is to catch the phugoid in a pitching up direction as you impact the ground – just as you would in a flare. Notice here, I do not say runway. This is because after several attempts the best I could do was place the cyber wreck within the confines of the airfield boundary. In the actual event the crew did manage to put the DC 10 on the runway, but the horrendous speed and high sink rate unhinged what has got to be one of the most impressive demonstrations of skill and courage in recent years.

Although there was a great loss of life, an amazing number of people survived – including the cockpit crewmembers themselves. In fact Captain Dennis Fitch, the pilot handling the throttles and thus flying the aircraft at the time was actually a ‘deadheading’ check captain who after teaming up with the primary crew in their dilemma, “flew” the aircraft from the flight engineers seat between the pilots! When this scenario was later replayed to his airline colleagues in the simulator, not one managed to get it right first time!

Maybe knowing your life is on the line was what made the difference. After recovering from his injuries Captain Fitch embarked on a worldwide lecture tour, sharing his experience with other airline pilots, visiting SAA in 1991. Which leads me to the gist of this article. Some emergencies are so outrageously improbable that they just can’t be trained for. Our only guidance comes from the experience of others. And sometimes this, coupled with good judgement, skill and courage are all there is to carry you through.

Over the years commercial aviation has seen a gradual shift in emphasis away from stick and rudder ability towards greater technical proficiency. Although understandable, the incidents described above confirm that even in the venerable high tech glass cockpit, the prospective airline pilot still needs good stick and rudder training and a thorough understanding of aerodynamic principles to help tackle what he can’t always be trained for.

Do I advocate aerobatic and gliding training to my airline students? Absolutely! And not only for the above reasons. Apart from the shear thrill of it, an understanding of an aircraft and a self-confidence is developed that one just can’t gain from any other type of flying. And you never know when those skills might just come in handy – even in an airliner!

The author is an A340 Training Captain with SAA and CEO of Flight Training College George.