Engineers call for grounding of A380 after cracks found in wings

by Grant Martin on

The Daily Mail reports this evening that cracks found in the wing sections of several Airbus A380 jumbo jets have led to deep concern among a group of Australian aircraft engineers. Calling for the grounding of all A380 aircraft, the group highlighted recent faults uncovered in the wing structures of several Singapore Airlines and Qantas jets in their complaint.

Acknowledging the cracks, the airlines and manufacturer claim that the faults are in non-critical sections of the wings and that an easy detection and repair method has been identified. None of the seven current carriers that operate the aircraft are planning on taking the equipment out of service.

Nevertheless, news of the cracks is a significant concern for Airbus, which has been struggling to compete in a market that’s quickly moving towards smaller, more fuel efficient equipment. With the earliest delivery of their next generation aircraft slated for late 2013 2014, they need to rely on sales of the A380 to propel revenue. If technical difficulties keep plaguing the A380, it could significantly impact the future of the company.

[flickr image via Jlcwalker]

United Airlines to order A380 jumbo jet?

by Grant Martin on

Things are going pretty well for United this year. Full approval for their merger with Continental Airlines went through, they became the first domestic carrier to adopt bio fuel and one of their biggest competitors has gone bankrupt. Their media and public relations departments should get the rest of the year off. In fact, they should buy us dinner.

In addition to all of that good news, rumors around the community are that the airline is eyeballing a new Airbus A380, the largest passenger aircraft on the market and a behemoth that’s usually only reserved for the major international carriers. Though United flies plenty of routes, the majority of their passengers fly short haul in the United States, and as such a heavy, fuel-guzzling aircraft is hardly worth the investment.

With growing focus in the Asian Pacific region, however, the airline may start investing in larger aircraft to serve that market. While they haven’t made any official announcement to lay public, Aviation Week reports that the COO of airbus claims “that United President and CEO Jeffery Smisek has changed his previously held view that the widebody was inappropriate for U.S. operators and now saw possibilities for the A380 in the new United fleet.”

Perhaps that means that the American carriers are finally willing to step into the long haul game. We sure hope so.

Cockpit Chronicles: There’s more behind the Air France 447 crash than pilot error

by Kent Wien on

Recently a couple of pilots found themselves in a situation that was foreign and perplexing to them; a scenario the designers of the airplane hadn’t fully expected. They fought their way for 3 minutes and 30 seconds while trying to understand what was happening after a failure of one of the pitot static systems on their Airbus A330. At times the flying pilot’s inputs exacerbated the problem when he assumed they were flying too fast rather than too slow.

Because they hadn’t seen anything like this in the simulator, and the airplane was giving conflicting information, the recovery would have been all the more difficult.

Pilots are taught that an erroneous airspeed indicator can be countered by paying close attention to their pitch and power. It sounds so simple that many pilots wonder aloud, just how anyone in the situation could mess it up.

In the early morning hours of June 1st, 2009, the pilots of Air France flight 447 were working their way around thunderstorms while flying from Rio de Janeiro to Paris in the widebody Airbus A330.

A faulty pitot tube created a situation where any changes in pressure resulted in fluctuations in the airspeed indicator. To understand how difficult it is to recognize this problem and then correct for it, let me use the following analogy:

Imagine you’re driving a car at night. You come down a hill and you feel the cruise control back off on the gas to prevent the car from going too fast. Just as you look down at your speed noticing that it is, in fact increasing, a siren and lights go off behind you. A police car has woken you up from your late night drive.

Instinctively you kick off the cruise control and apply the brakes. The speedometer indicates you’re still accelerating, so you press harder on the brakes. Your car has now decided that because you’re trying to slow so quickly, it will shut off the anti-skid braking system and allow you to use manual brakes. You then skid off the road and into a ditch.

Based on the released information about one of the most mysterious accidents in recent history, it appears the pilots of Air France 447 faced a set of circumstances similar to our driving example.When flying in turbulence, it’s important to watch your airspeed. Flying too fast will result in a situation called mach tuck, where the nose can slowly pitch over and the controls lose their effectiveness.

Flying too slow can result in a stall. Not an engine ‘stall’ as might be incorrectly reported by the press, but an aerodynamic stall where the wings aren’t developing enough lift, and an immediate increase in the airspeed is needed to recover. Here’s a tip for reporters. In aviation, the term ‘stall’ will never be used to describe engines that fail. Ever.

Up at altitude, the difference between flying too slow and too fast can be as little as 20 knots. It’s called the ‘coffin corner,’ a morbid term used to describe narrow band of airspeed that we need to maintain.

In this 767 example above, the airplane has a very safe margin between
too slow and too fast, as shown on the airspeed indicator on the left.

While working their way around clusters of cumulonimbus clouds in the inter-tropical convergence zone that night, our two first officers (the captain was in the back on his planned rest break) did their best to stay away from the weather.

A side note: whoever takes the second break is usually the pilot who made the takeoff and who will also make the landing. So the relief pilot (who’s a type-rated copilot) took over the flying related duties while the captain slept.

Back to the flight: During turbulence, maintaining that speed can be more difficult, much in the way it’s tough to hold the speed in a car going over hills. You may look down after studying the weather only to notice that the auto throttles aren’t holding the .80 mach speed you have selected and the airplane is now at mach .83 and accelerating. In a moment, the clacker goes off, indicating you’re now exceeding the normal cruise speed of the airplane, which certainly gets your attention, much like the sirens of the police car in our example.

In the case of Air France 447, the autopilot kicked off in response to the overspeed, and was followed by a warning Airbus calls a ‘cavalry charge’ sound which is designed to get your attention quickly. About 30 seconds later the auto throttles were turned off manually and the throttles were pulled back, but it takes an eternity to slow down such a slippery airplane, and it may have seemed to the flying pilot that he was still accelerating anyway. So he pulled the nose up, an effective way to slow down in a critical situation like this. (See last week’s post on the eight ways to slow a jet.)

Amazingly, as the airplane climbed from 35,000 feet to 38,000 feet the airspeed continued to increase, at least that’s what it looked like on the flying pilot’s side of the airplane. He must have been surprised then to hear the stall warning activate moments later, indicating that they were flying too slow.

The other pilot likely noticed the airspeed on his side was decreasing, and perhaps because he saw the difference between both airspeed indicators, he’s heard to say on the recording that “we’ve lost the speeds.”

They had slowed from 275 knots indicated to 60 knots, at which point the airplane went into a mode called ‘alternate law’ which meant the automatic protections that kept the airplane from stalling were removed.

To make matters worse, the stabilizer trim moved from 3 degrees to 13 degrees nose up, which meant the airplane may have needed almost full nose down inputs on the stick just to fly level.

And to further confuse and confound the pilots, it’s recently been reported that as the airplane slowed further, the stall warning stopped. When max power was applied and the nose was lowered at one point, the stall warning came back. This is opposite of what the pilots were looking for in a recovery.

The airplane ‘mushed’ in a 15 degree nose up attitude all the way to the water, at a rate of 11,000 feet per minute.

We occasionally train for unreliable airspeed indications, but it isn’t covered during every recurrent training period. Stall training is often limited to the low altitude variety, which is far less critical than one occurring at 35,000 feet. I’m certain training departments all over the world will soon be required to train for high altitude stall recoveries.

Since this will take some time to become a requirement, on a recent simulator session, I asked my instructor to give me a loss of airspeed scenario at altitude. I told him I’d prefer to have the failure at any random point during our four hours of simulator time that day.

When he eventually failed it, causing the airspeed to slowly increase, I immediately pulled the throttles back and raised the nose a bit. The non-flying pilot simply said ‘airspeed’ which I thought was obvious, as it appeared to me that the airplane was accelerating rapidly and I was doing my best to get it back under control.

But on his side, the airspeed was dropping rapidly. When he said “airspeed” he actually meant that the airspeed was slowing and that I needed to do something about it. I finally looked over at his side, and saw that his speed was actually decreasing while mine increased. This all occurred within ten to twenty seconds.

I immediately lowered the nose and told him that I suspected my airspeed indicator had malfunctioned. Since my indicator was useless, I offered the airplane to him.

It’s easy for pilots to harp that “pitch and power equals performance” but it’s not easy to ignore the instruments you’ve trusted for thousands of hours. For the pilots of Air France 447, the incorrect airspeed indications and confusing stall warning sounds that were caused by a failure of the pitot static system proved to be too much to handle.

Furthermore, the Airbus design reinforced ideas that counter everything a pilot is taught, Specifically, these pilots learned that pulling the stick full aft would not result in a stall when the airplane was operating under a condition known as “normal law.” Much of their careers had been flown in airplanes with this feature. That night, after the initial climb, they were operating under “alternate law” which allowed far greater changes to the flight envelope, and removed that protection.

I wouldn’t have wanted to be in their shoes.

Much of the focus of the accident in the press has been to blame the pilots for clearly stalling the plane. One strange headline read “Baby pilot at the controls of AF 447.“

The ‘baby pilot’ was actually 32 years-old and had previously flown an A320 for 4 years and the A330/340 for just over a year. He had 2,936 hours of flight time with 807 hours in the A330/340.

The other copilot, at age 37 had 6,547 hours with 4,479 of them in the A330/340. Sadly, his wife was also on board the aircraft as a passenger.

And the 58 year-old captain, who came to the cockpit from his break halfway through the event had 11,000 hours of which 1,747 were in the A330/340.

I’ve said it before; in the eyes of the media, pilots are either heroes or villains depending on the outcome of the flight. These pilots faced challenges few of us have ever come across. Given the mechanical failures that started the chain of events, there’s certainly plenty of blame to go around. Events like these have a profound impact on our training and help prevent future accidents. And at least that is something we can be thankful for.

In case you’re interested in even more details, AvHerald has an excellent summary of the BEA preliminary Air France 447 accident report.

Cockpit Chronicles takes you along on some of Kent’s trips as an international co-pilot on the Boeing 757 and 767 based in New York. Have any questions for Kent? Check out the Cockpit Chronicles Facebook page or follow Kent on Twitter @veryjr.

Cockpit Chronicles: Eight ways to slow a jet

by Kent Wien on

One of my first posts on Cockpit Chronicles was an explanation on how to park a 757. At the risk of catering only to people who have recently acquired their own Boeing jets, I’d like to continue with another lesson.

The eight ways to slow a jet

When you’re driving your 5-speed manual transmission car and you exit an offramp, besides just taking your foot off the gas pedal, there are a couple of different ways that you can slow down. Most people probably put on the brakes, but you could also downshift as well.

In an airliner, there are four different ways inflight and four methods on the ground to slow a jet, and often these techniques can be used in conjunction.

Unlike turboprop airplanes, jets are rather difficult to slow down and require a bit of planning in advance to avoid burning too much fuel or ending up too high at the airport for landing.

So let’s start with our Boeing that’s at 33,000 feet. Pilots will use a rough “3 to 1” guide when deciding when they’ll need to start down, adjusting for wind as needed.

To do that, take the 33,000 feet, drop the zeros and multiply it by three. 33 X 3 = 99 miles.

So, for a descent at idle thrust, the pilots will need to start down within 99 miles of the airport. Any later and they’ll be too high and need to add drag to get down, and any sooner and they may need to add power and level off for a while. Either way, more fuel is burned.

A side note: If the engines were to fail, our airplane would likely be able to make it to the runway if it were within that 99 mile point. It’s just going to take some perfect planning on the part of the pilots, as was the case with the Air Transat and Air Canada flights.

Since an airplane burns far less fuel at altitude, it’s best to stay up high until the airplane can descend, ideally at idle thrust, all the way to the final approach segment. That’s our goal, subject to air traffic control requiring something different.

It’s not uncommon, especially in the U.S., for air traffic controllers to leave you at altitude past your normal beginning of descent point. In this case, it’s going to take more than idle thrust to descend quickly enough.Speed Brakes

In this situation, we can use speed brakes, which are the panels on top of the wing that move up equally on both wings to increase the drag on an airplane and reduce the lift.

So they’re the best method to initially increase the rate of descent and/or slow the airplane.

Since there are usually no airspeed limitations when using speed brakes, they can be deployed anytime they’re needed.

Flaps

The next method to slow an airplane involves using the flaps. These devices are panels that extend from the leading and trailing edges of the jet to change the shape of the wing to provide more lift. This allows a high-speed wing to quickly transform into a wing that can keep the jet in the air at much lower speeds.

In addition to creating more lift, flaps also create drag, and can slow a jet nicely. Unfortunately, we can’t begin to use the flaps until below 250 knots or so. Each step of the flaps has a different speed limit, above which too much stress will be placed on the flaps and a maintenance inspection would be necessary if that limit were exceeded.

We now have a program called FOQA, or Flight Operations Quality Assurance, that records the exact speed at which the flaps are deployed among many other parameters and sends a report to the company (see my personal experiences with FOQA here). Should the flap speed limits be exceeded, the airplane is taken out of service and given a thorough inspection, sometimes costing tens of thousands of dollars in maintenance man-hours to accomplish, not to mention the revenue lost when an airplane isn’t flying.

So let’s say that we’re flying into Miami or Los Angeles which are two airports known for the ‘slam dunking’ that ATC occasionally needs on certain arrivals.

Imagine that you’re now at 230 knots with the first notch of flaps extended and you still aren’t descending at a high enough rate. What can you do? More flaps would add drag, but you’ll need to be below 220 knots before you can go to flaps 5. And you’d better not hit a gust or any turbulence that sends you above 220 with those flaps out.

Landing Gear

So the next solution is the landing gear. This can be extended at any time you’re showing 270 knots or less of airspeed. They add a similar amount of drag as the spoilers, which are still extended in our scenario.

Pull up, pull up!

Finally, as with any airplane, our 4th method to decelerate is pretty basic; lift the nose up which initially decreases our rate of descent. We adjust the descent to slow the aircraft to bring the flaps out on schedule.

Often times there are points along an arrival where we’ll need to be at a certain speed and altitude. These ‘crossing restrictions’ are very important to meet and add another challenge for the arrival.


Pull Up, Pull Up!

Fortunately we don’t have to rely only on the 3 to 1 calculation to properly meet these targets when planning our descent. We can plug in the speed and altitude we want when flying over a waypoint into the FMS, or Flight Management System, that will calculate the time we should start down, using a function called VNAV, or Vertical Navigation.

Slowing down after landing – Ground Spoilers

Finally when we touch down, ground spoilers will automatically deploy from the top of the wings. This is done by using the same handle which deploy the same panels as the speed brakes, but now a few extra panels that open even further than the speed brakes are included.

These panels not only give us added drag, but when deployed, they add weight to the wheels which dramatically increases the effectiveness of our second method of stopping, the brakes.

Brakes!

All airliner brakes have anti-skid protection and the option to use ‘autobrakes’ for landing. We can preset the brakes before landing to automatically activate soon after we touch down. There are five different levels to choose from, with ‘max auto’ the one to use on slick runways. The same setting on a dry runway would leave a nose print in the setback in front of you, however.

To manually operate the brakes, pressure is applied to the top of the rudder pedals with your toes which, if they were selected, will also kick off the autobrakes. We generally don’t manually apply brakes until we’re below 100 knots. Pilots can even control the right and left brakes independently by pressing the tops of the right or left rudder pedals.

Reverse thrust

The noisiest, and third most effective way to stop an airplane on the ground is to use reverse thrust. This is done by lifting some handles that are in front of the thrust levers (throttles) when they’re at idle. The farther we pull these handles, the more thrust is deflected forwards to slow the jet. If these devices are inoperative, or a specific airport has restrictions on their use during late night hours, only 400 to 600 extra feet are needed for landing.

As we slow through 80 knots, we’ll bring the reverse thrust to idle and coming through 60 knots we are advised to stow the reverse thrust sleeve completely.

Here is a video of the reversers in operation that I caught while mechanics were making adjustments.

All of these methods can be seen in this picture of the center console of a Boeing 757:

Aerodynamic braking

There’s actually a fourth method of slowing an airplane after landing, but it’s generally not effective in the airline world, and more often seen when watching the Space Shuttle land. Aerodynamic braking is when the nose wheel is held high off the ground to use the drag of the airplane as a way to slow down. It’s not really effective, and it delays our ability to use brakes (and reverse thrust on the MD-80) while the nose wheel is still off the ground.

To taxi to the gate, the captain will use a combination of throttle and brakes to control the speed, which the FAA says shouldn’t exceed that of a person walking briskly. In reality, five to fifteen knots while taxiing is far more common.


So there you go. Oh, and congratulations on your recent jet acquisition. Or for those of you just worried about an Airport ’75 event occurring on your next flight, this could come in handy.

Either way, stay tuned for some more obscure airline flying tips!

Cockpit Chronicles takes you along on some of Kent’s trips as an international co-pilot on the Boeing 757 and 767 based in New York. Have any questions for Kent? Talk to him on the Cockpit Chronicles Facebook page or follow Kent on Twitter @veryjr.