If AF447 had had 737 MAX’s MCAS

Recently there was a fascinating piece by Bjorn Fehrm on LEEHAM News and Comment explaining why Boeing had installed an automatic trim system (MCAS) on the 737 MAX to intervene aggressively should the aircraft be in danger of stalling even with the autopilot disconnected.

The reason for this was that though the 737 as originally designed was naturally stable it sat very low on the ground to facilitate loading at airports with then limited facilities. The bottom of the engine nacelles had to flattened to allow this. However, in order to install the much more efficient larger diameter engines for the 737 MAX, they had to be moved forward. As explained by Fehrm, this was fine at normal angles of attack, but should the angle of attack become too steep the nacelles themselves would produce lift far forward of the centre of gravity, which might result in a disastrous stall with the nose being pushed up further and further. To preclude this, Boeing installed MCAS, the Maneuvering Characteristics Automation System to force the nose down.

Unfortunately, in the Lion Air crash, the pilots did not know that unlike in the previous version of the 737 the forced down trim could not be removed by pulling back on the control yoke–the STAB TRIM CUTOUT switches have to be set to CUTOUT, which is what the pilots did when the same thing happened on an earlier flight of that aircraft.

Interestingly, in another post we cited the case of the XL Airways/Air New Zealand acceptance test flight, that crashed because the pilot could not overcome the upward maximum pitch trim and upward leverage of the low-slung engines causing the aircraft to stall will insufficient height to recover. In that case, two-out-of-three of the angle of attack sensors had frozen at the same angle and the computer dismissed the odd man out. In the Lion Air crash it seems the MCAS was triggered by just one angle of attack sensor showing too steep an angle, which was quite reasonable because the high pitch indicated by one might have been genuine and it was a precautionary measure, and better safe than sorry. If the pilot had been aware of what he should do, or thought of it like the pilot on a previous flight on that aircraft, there was no reason for it to crash.

It is a pity Air France Flight AF447 that crashed into the South Atlantic did not have something like MCAS both stopping the pilot stalling the Airbus A330, and preventing him from impeding recovery by pulling back continually on his sidestick.

 

         

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Comparing Lion Air 737 MAX Crash in Indonesia and Fatal XL Airways/Air NZ Acceptance Flight #LionAircrash

Like the Lion Air 737 MAX crash in Indonesia, the crash of an A320 acceptance test flight in France in 2008 involved the extreme trim of the horizontal stabilizer that the pilots could not overcome. See Chapter 18: Not All Pilots can carry out Test Flights.

The A320 pilots attempted to check the automatic stall protection system at too low an altitude with little height to recover should something go wrong.

Unfortunately, the angle of attack sensors due to ingress of water used to clean the fuselage had frozen in the level-flight position making the computer believe the aircraft was not going to stall.
When it eventually did stall, the extreme upward trim of of the horizontal stabilizer made it impossible to push the nose down to regain speed, for with the low-slung engines at full thrust also pushing the nose up, 
the elevators could not overcome the two. The stalled aircraft (not filled with fare-paying passengers) plunged into the sea. 

In the Lion Air case, the downward trim came about because a new safety system (which no pilots had been told about) pushed the nose down because of a faulty angle of attack sensor indicated that the aircraft was was nose-up and in danger of stalling.

WHAT THE TWO ACCIDENTS HAVE IN COMMON is failure of the pilots to deal with the extreme trim of the horizontal stabilizer and therefore being unable to recover.  

In the A320 case, there was a warning to USE MANUAL TRIM, which the pilots either did not notice or ignored–they anyway had little time.

In the 737 case, it was not so simple as the computer overrode the trim system even in manual, and the trim had to be completely disabled. The pilots did not even know that they should do that, though on when problems had occurred with that very aircraft on a previous flight the pilots had managed to do so and recovered. Unfortunately, the the pilots of the crashed flight were not told about that how those pilots had disabled the trim.

We highly recommend the reader click HERE to see the fascinating article by Bjorn Fehrm on Leeham News explaining why Boeing introduced their new anti-stall system on the 737 MAX to cope with the forward positioning of the larger engine nacelles covering the higher bypass LEAP-1B engines–the 737 conceived many years ago was designed to be very low on the ground, hence the odd (not round) shaped nacelles. 

For reference
Boeing’s just issued warning to users of the 737 MAX that was not in any of the manuals.

“This bulletin directs flight crews to existing procedures to address this condition. In the event of erroneous Angle of Attack (AOA) data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC. It is possible for the stabilizer to reach the nose down limit unless the system inputs are counteracted completely by pilot trim inputs and both STAB TRIM CUTOUT switches are moved to CUTOUT.

Additionally, pilots are reminded that an erroneous AOA can cause some or all of the following indications and effects:

– Continuous or intermittent stick shaker on the affected side only.
– Minimum speed bar (red and black) on the affected side only.
– Increasing nose down control forces.
– Inability to engage autopilot.
– Automatic disengagement of autopilot.
– IAS DISAGREE alert.
– ALT DISAGREE alert.
– AOA DISAGREE alert (if the AOA indicator option is installed)
– FEEL DIFF PRESS light.

In the event an uncommanded nose down stabilizer trim is experienced on the 737 – 8 / – 9, in conjunction with one or more of the above indications or effects, do the Runaway Stabilizer NNC ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.”

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United Airlines “Fuel Emergency” 787 Landing at Sydney

Unlike the Avianca crash at New York in 1990, the United Airlines flight declaring a FUEL EMERGENCY on landing at Sydney seemed to have had fuel for another attempt, if not two attempts, to land should they have had to go around. They were no doubt following the airline rules to the letter and should be congratulated.Declaring a fuel emergency ensured air traffic control would do all possible to avoid them having to go around, say because of another aircraft staying longer than expected on the runway.Had they had to go around, something else might have occurred, delaying a landing, with the fuel safety margin getting tighter.

They extract below from our piece on the Avianca incident shows what can happen, though in that the copilot did not declare it was an absolute emergency as it was their last chance to land.



Extract:

Avianca 52 Copilot Failed to Say “Emergency” (New York, 1990)

The survivors and relatives of those who died when Avianca Flight 52 ran out of fuel while attempting to land at New York’s JFK airport were incensed when reminded the official inquiry attributed the accident almost entirely to the first officer’s failure to use the term “emergency” in his radio transmissions to air traffic control.

Avianca Flight 52, January 25, 1990

The lights in the passenger cabin of the Colombian Avianca Boeing 707 flickered as the fuel supply to the engines became erratic. With so little fuel left, no measure could save them other than coming down on a runway or flat, open space. However, JFK airport was fifteen miles away, and the hilly ground of the affluent residential district of Cove Neck, on Long Island, lay ahead.

A few seconds later the engines fell silent, leaving only the rustle of the wind against the fuselage, soon to be drowned out by the screams and exclamations of the passengers realizing they might be facing their maker.

How, in what one would imagine to be one of the most sophisticated air traffic control (ATC) zones in the world, could the pilots and passengers of Avianca Flight 52 find themselves in such a predicament? It was due to what, with hindsight, was a whole series of missed opportunities to avoid disaster.

The first of these was not diverting to their alternate, Boston, when, on approaching the New York control zone an hour and a half earlier, controllers informed them their wait in the holding pattern would be at least forty-five minutes. The pilots possibly thought the controller was being careful and that the wait would not be very much longer. In fact, they had to hold for seventy-seven minutes.

Then, as the aircraft was subsequently handed over from one controller to another, the first officer, who was handling radio communications, used phrases such as “We’re running out of fuel.”

He evidently thought this clearly indicated their fuel predicament, but he failed to convey the true situation to the controllers, who had perhaps fifty aircraft in the sky, all in a sense running out of fuel and all wanting priority. If they started to let aircraft that had not declared an emergency jump the queue, a traffic jam would develop over the airport, perhaps compromising the safety of other aircraft also low on fuel.

Another factor explaining the controllers’ apparent lack of probing into Avianca 52’s status was that, with the aircraft being handed over successively from controller to controller, none had the time to build up a detailed picture. Aircraft have to be pigeonholed in the controller’s mind, and this is particularly so at busy times; for them it is either a normal flight or declared emergency.

When after seventy-seven minutes Flight 52 was allowed to exit the holding pattern (after the crew were asked how much longer they could hold), it was passed on to the approach controller, who, unaware of their predicament, greeted them as follows:

21:03:11 Approach:
Avianca zero five two heavy, New York Approach, good evening. Fly heading zero six zero.

After acknowledging this, the Avianca flight crew, consisting of the captain, first officer, and flight engineer, agreed on the need, when less than a thousand pounds of fuel remains in any tank, to avoid doing anything, such as raise the nose too much or accelerate violently, that might cause it to slosh to one side, leaving the outlet uncovered.

The tower controller, who was about to hand over to a colleague at the end of his shift, simply handed them over to the approach controller.

The captain told the first officer to tell approach they didn’t have fuel, but the first officer, after automatically acknowledging the order to climb and maintain three thousand feet, reverted to saying, “We are running out of fuel, sir.” The controller replied “Okay” and gave them a new heading.

Again, the captain asked the first officer if he had advised ATC they didn’t have fuel. He confirmed that he had, adding optimistically, “And he’s going to get us back.”

The approach controller then gave instructions to two other aircraft. After giving Avianca 52 a new heading, he showed his concern as one can see from the following exchange.

21:26:35 Approach control:
Avianca zero five two heavy, ah, I’m going to bring you fifteen miles northeast and then bring you back onto the approach. Is that fine with you and your fuel?

21:26:43 First officer:
I guess so. Tha [sic] you very much.

The captain asked what the controller said, but before the first officer could tell him, the flight engineer bizarrely said,

“The guy is angry.”

End of extract.

Click HERE for Table of Contents

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AF447 Documentary on More4 TV



 The More4 TV documentary was good as far as it went but did not include contributory factors such as the captain only having had an hour’s sleep the night before, the poor relationship between the two copilots, and the fact that the captain was probably not in his bunk.

These and others are detailed in our account.

Click HERE for Table of Contents

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Why hardly any hosepipe bans in UK?

Why hardly any hosepipe bans?

A ban would reduce the UK water companies income. They seem to prefer to hold off imposing a ban at the risk of having to impose a much stricter one later, or even having to ration supplies.

It was a good call in 2018 for just when an increasing number looked inevitable, the rain came.

Apart from the risk of having impose stricter bans, or even ration supplies, later, this seems fair in that really poor people would not use much more water while the very rich with big gardens and lawns (and water meters?) would pay more, and be able to do so.

Of course this depends on people having meters.

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XL Airways-Air New Zealand Acceptance Flight

In updating Air Crashes and Miracle Landings we added this disastrous test flight because it had so many lessons for pilots and programmers of fly-by-wire systems. The lessons learned most likely saved lives on revenue flights. Extract:

Not All Pilots Can Conduct Air Tests (Off French Med. Coast, 2008)

What was expected to be a mere formality turned to disaster

 

This highlights the danger of pilots who are not test pilots carrying out tests without defining what constitutes a pass or fail, and the problems a pilot can face on taking over manual control from the computer.

XL Airways Flight 888T, November 27, 2008

 

Faced with a refusal by the air traffic controller at Bordeaux on the French Atlantic coast to allow them to  engage in test flights in general air traffic, the pilots of the Airbus A320 had cut short their “acceptance flight” and turned back to Perpignan Airport on the Mediterranean. In just under an hour—half the time intended—they had surreptitiously managed to fit all but one of the tests into their flight plan without air traffic control objecting.

 

Extract continued:

….
The elevators (operated via the sidestick) could not overcome the combined effect of the pitch trim set at its maximum nose-up and the go‑around thrust of engines set low down under the wings also levering the nose up.

At 15:45:42, after rising enough for the stall warning to stop momentarily, the airspeed had fallen to 40 knots. Two seconds later the maximum values recorded were a pitch of +57 degrees (i.e. exceedingly nose up), and an altitude of 3,788 feet, at which point the aircraft lurched over and careered down into the sea. All on board, including three Air New Zealand engineers and a New Zealand Civil Aviation Authority official in the passenger cabin, were killed.

Only sixty-two seconds had elapsed between the time the stall warning first triggered and the moment the recordings stopped!

The Investigation

This crash was very troubling because a month earlier another Airbus, a Qantas A330, had behaved very bizarrely (see Chapter 17) off the coast of Australia, albeit with the pilot managing to recover. After first suspecting the Air Data Inertial Reference Units as the Qantas A330 investigators had done, the French investigators were able to show the cause was the freezing of the water in the mechanisms of the two angle of attack sensors on the left of the fuselage. A third sensor still working was ignored by the system on the “odd man out” principle.

END OF EXTRACT

Click link to —> Table of Contents

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Heathrow Airport Expansion Security Risk?

 

Even with the best security checks at airports with flights to London’s Heathrow, it would be impossible for not one in hundreds of thousands to miss an explosive device.

Again, aircraft could crash on the city for other reasons.

We are talking about flights continuing for years and years, so the risk though small would be greatly multiplied and significant.

An airport in the Thames Estuary area as suggested by Boris Johnson may one day seem to be a chance regrettably missed. 

The inquiry dismissed the idea out of hand. Admittedly it was not popular with the airlines.

There were other options.

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Seeing MH17 in Perspective

The outpouring of criticism of Russia almost invariably includes mention of the mention of the “dastardly” shooting down over the Ukraine of Malaysian Airlines Flight MH17 in 2014.

Russia was presumably ultimately responsible, whether or not it was their own people who were handling the BUK missile launcher, since they supplied the equipment. Nevertheless, it was obviously a mistake.

The late, and much missed Australian aviation journalist, Ben Sandilands, made the point that though the Ukrainians–keen to get revenue from overflights–said airliners could fly there so long as they kept above 32,000 feet, they should not have been doing so as failure of an engine would mean they would not be able to maintain that height.

To be fair, we should not forget that when the USS Vincennes, a multi-billion-dollar US warship chasing rag-tag gunboats, mistakenly shot down an Iranian Airliner in the Persian Gulf in 1992, the US government obfuscated and muddied the waters to deny responsibility (just like the Russians are doing).

They finally paid out $61.8 million in compensation to discontinue a case brought by Iran against the US in the International Court of Justice in 1989, all the while not admitting responsibility.

 

 

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Siberian Flight Corridor

 

I still remember flying the very long southern route from London to Japan and then the quicker route via Anchorage taking eighteen hours or so.

Now there is the non-stop route via Siberia taking about twelve hours–11.40 Eastwards; 12.30 Westwards.

However, until seeing the fascinating little video below there were things about the route I did not realise.

The Russians, aware of the valuable card they hold, charge as much as $100 per passenger per return trip, though details are confidential. 

Apart from the UK, where Virgin and BA were given permission, only one carrier per European country was allowed.

This means legacy carriers such as BA, Air France, Lufthansa, KLM, and SAS monopolize the route.

Though the high charge coupled with high air passenger duty, say from London, would make life difficult for low cost carriers, Norwegian has applied but been refused.

See video:

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USS VINCENNES Accidently Shoots Down Iranian Airliner

The account is typical of so many air crashes in that it resulted from a whole series of misjudgements, errors and unfortunate circumstances.

The inquiries faced the dilemma that if they faulted the crew, captains might in future hesitate to defend their ships.  

_____________________________________________________

Many readers are using Kindle Unlimited which may not allow them to post reviews–though we do cleverly get paid according to the number of pages read!

For your information an (unfair?) US 2-star review was as follows:

29 April 2018 – Published on Amazon.com
Format: Kindle Edition
Interesting compilation of famous airline accidents, spoiled by the middle of the book by a shrill polemic attacking the U.S. Navy and the crew of the USS Vincennes, and deteriorating to claims of governmental coverups and the incompetence of police and investigators. There are also startling neologisms and amazing vacuoles of ignorance. One example of an unintentionally funny confabulated “fact” is about a pilot named Gibson with a nickname of “Hoot”, attributed by the author to a role as an owl in a school play. I should have stopped reading while it was still credible.

1. Things complained about are at the end of the book not the middle.

2. Vincennes material as stated largely based on research by Newsweek.

3. “Hoot” not a funny confabulated fact, but taken from a great book on the affair, though tired of being asked about his nickname, Gibson suggested in the occasional interview it was derived from that of a famous actor.

Any well-considered review on Amazon.com to compensate would be greatly appreciated.

On the other hand, the 5-star review in the UK was:

Andy–5.0 out of 5 stars

“The new MacArthur Job has arrived.”
Mr Bartlett has taken over the mantle of the late, great MacArthur Job, as an aviation writer of undoubted excellence.
His book covers many, many accidents, both well known and obscure, in just the right amount of detail to remain fascinating.

The only negative thing I can say is that he seems to have a great disrespect for Captain Sullenburger. Often deriding Sully’s piloting skills whenever the opportunity arises.

And TWA 841 was a 727, not a 737, an accidental typo no doubt, as was a quote on the same page dated 1971 instead of 1979.

[We corrected the typos, removed some gratuitous references and rewrote the end of the account of Sully’s ditching to better explain we meant the MIRACLE  lay both in the ditching and in the rescue from the water.]

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