Around the Pattern

Ramblings about flying for fun and profit.

Tag: Airbus A-330 (Page 1 of 3)

The AF 447 Black Boxes

I’m sure  that by now you have read all about the recovery of the flight recorders from the Air France A-330 crash in the Atlantic in June 2009.  There have been several articles about the information they are releasing from the data analyses.  Here is one from the Wall Street Journal that was published a couple of days ago. Here is one from today on the AvWeb site Most of the information from the latest AvWeb article comes from an update to the investigation published by the BEA (the French Aeronautic Agency doing the investigation). A pdf file of the BEA update is here and on the AvWeb site. Northwest Airlines Airbus A-330 If you read the BEA report and are not familiar with the terminology – PNF refers to ‘Pilot Not Flying’ and PF refers to ‘Pilot Flying’ – a way the cockpit duties are assigned once the aircraft starts the take-off. Captains and co-pilots (First Officers) often trade off duties on consecutive legs of a trip. This time it was the co-pilot’s turn to fly.

If you read the report and have any questions about terms or phrases – leave me a comment and I’ll try to clear up the terminology for you.

Once again – I wasn’t there (obviously), I have no first-hand knowledge of what went on in the cockpit nor do I have access to the actual flight recorder data or cockpit tapes. Even so, I thought I’d make a couple of comments.

In the ‘Final Minutes’ graphic in the Wall Street Journal the note mentions the nose being ‘pushed up’ which confuses me a bit. It was obviously not written by a pilot if they are implying that control inputs were the cause if the increased pitch.

The Airbus A-330 is an ‘electric jet’ –  meaning it is controlled by computers. The controls in the cockpit are not physically connected to anything directly controlling the flight control surfaces nor the engine. Everything is done through position and force sensors. The computers controlling the airplane read the forces and positions from the pilot’s movements of the control stick and power levers. The computers  analyze that information and then decide if the control movements that they imply are within the ‘laws’ programmed within their software. If the computers think the request is ‘legal’ they will move the control surfaces and/or change the power setting to match the request.

In the computer operating mode referred to as ‘Normal Law’ there are extensive safeguards enabled – such as the inability of the pilot to input control movements that will allow the aircraft to stall or overspeed.

Increasing systems failures may degrade the operating mode from ‘Normal Law’ to ‘Alternate Law’ to ‘Direct Law.’ As those systems degrade, so do the protections built into the flight control system that control inputs cannot override. In Alternate Law there are still some protections in place, but they act in a different way – and pilot inputs can override the protections. In Direct Law there are no computer-generated protections in effect. There is then a direct relationship between the cockpit control movements and the flight control surfaces – though still through the computers.

The only time that the aircraft is intentionally operating in  a mode close to Direct Law is during the landing flare (a condition called ‘Landing Mode’) – that is so that the pilot has some semblance of normal feel and control feedback during the landing.

While the plane is cruising along at FL350 it is in Normal Law with all the aerodynamic protections of the system in operation.  If the computers, for whatever reason, were to think that the airplane is  flying too fast – up near it’s maximum mach number at that altitude –  they would take actions to protect the airplane. Those actions could include a reduction in power and/or a pitch up to reduce the speed. If the computers thought the plane was flying too slowly it could increase the power to maximum and try to lower the nose.

With the system degraded to Alternate Law and the autopilot and autothrottles disconnected it is up to the pilot to keep the plane upright. Hand flying a plane in the traffic pattern and hand flying the plane at FL350 are vastly different exercises. Then add to that the lack of tactile feedback from the side stick and you multiply the difficulty. The side sticks physically move very little compared to ‘normal’ aircraft control sticks and they have a centering spring that tends to return it to the neutral position.

The Airbus does not take lightly one pilot trying to help the other one with the controls. There is a light and warning visible on the glareshield when both pilots are making control inputs. You can’t tell what kind of inputs the other pilot is using, only that they have used some force on the stick to move it from it’s center position.  The two pilot’s inputs to the controls are added together and the result is sent to the computers. If both pilots pull the stick half way back the computer assumes that you want full back stick. If one of the pilots pulls full back and the other pushes full forward the sum is zero and the controls don’t move.

Now there are calls being made to change the airline training system to include more hands-on experience. It isn’t just the training system that needs to be changed. There also needs to be a change the jet transport philosophy of flying. When autoflight systems became more reliable and accurate the emphasis changed from hand flying the airplane to managing the autopilot.

I can remember going through training in the first versions of the 747 as a copilot and spending the majority of my simulator sessions hand flying the plane while also handling the radio communications with Air Traffic Control. The captain and flight engineer would be handling the malfunction and checklists. There was no requirement to use the autopilot and as I remember it was implicitly discouraged.

By the time I moved to the left seat of the smaller Airbus A-320, then to the right seats of the more automated B-747-400 and then the Airbus A-330, the emphasis had shifted completely. You were required to use the automation to the fullest extent. My impression was that the automation was so complex and capable that philosophy was that the more you used it the more familiar and comfortable you would be with its operation. But that familiarity comes with a price – the deterioration of hand flying skills.

I’ve stated my feelings about relying on automation in previous posts about being a systems operator rather than a pilot. And it seems that I’m not alone in my feelings based upon this opinion piece from a 747 pilot.

Was the lack of hand flying skills a factor in the Air France accident?  Maybe the final report from BEA will say.

 

Added 6/1/2011

I didn’t see this particular episode of  ‘The Early Show’ where ‘Sully’ Sullenberger was a guest, but this article on the CBS News site relates the opinions Captain Sullenberger expressed concerning the new information that has been released.

And here is an article from Jetwhine where Rob Mark gives his views on the newly released information.

A Challenging End to the Trip

Airbus A-330 takeoff On the final leg of my trip I was in the seat for the last 2/3, having taken the first break. I usually try to take the break that has me sleeping near the right time for my home time zone. Copilots get either the first or last break since the captain will be in the left seat for both the takeoff and the landing.

Our A-330 aircraft configuration currently has the pilot bunk located between the cockpit and the forward galley. That location makes it easy to get to and from the cockpit but its not so good for the first break. That period is when the flight attendants are doing their main cabin service which means, more often than not, that they will be banging galley carts into the bunk room wall. That in itself is bad enough, but the bed folds down from and is firmly hinged to that wall. I have had a cart hit the wall so hard that I bounced  up off the bed.

There is a project underway to change the aircraft configuration to relocate the pilot bunk in ‘the basement’  between the cargo compartments, across from where the flight attendant bunk is now located. That will provide room for a second pilot bunk and allow the double crew that is required for flights exceeding 12 hours – which explains why the company is willing to spend the money for the change. So much for the security aspects of the relief pilots being half way back in the plane.

The flying part of the leg was enjoyable and challenging. Our route took us as far as 67 degrees north. For most of the flight it was night time off the right wing with a full moon in view while off the left wing the sun was just below the horizon. As we got to north-central Canada and started turning south we eventually came to the point where the sun became fully visible.

The A-330, as all FMS-equipped aircraft, computes and displays a point where a descent should begin in order to meet and restrictions that are present in the instrument arrival procedure for the destination airport. Our arrival had a crossing restriction at one point of 12,000 ft at 250 knots. The FMS assumes that you will make an idle power descent at 290 knots and uses the forecast winds to work backward to our cruising altitude of FL410.  At that point the FMS places a little downward pointing arrow to tell you to get the descent started. The Airbus will not initiate the descent by itself.

It was my turn to get an approach and landing, so as we approached that down arrow I asked the captain to request a lower altitude. Of course the ATC response was Standby. Just as we got to the descent point we were given  descend to FL390, expect lower in 50 miles. Getting behind in the descent at altitude is certainly not unusual and, in most cases is easily recoverable. The FMS calculation does not take into account using the speedbrakes for added drag and a greater descent rate. Also, unless you have an additional restriction from ATC you can always increase your speed, which at idle power means a steeper descent. One of the pages on the FMS display gives a calculation of how far off the calculated descent path you have deviated. By the time we were given a descent directly to that 12,000 foot restriction we were over 5000′ above the calculated profile. Idle power, full speedbrakes and holding 320 knots got us to the altitude and slowing through 270 knots as we crossed the fix. The captain had negotiated the deletion of the speed restriction in anticipation of our not being able to comply – thinking ahead is always good.

Before we started the descent I had briefed the instrument approach that I expected us to be assigned. Our destination has three parallel runways and 99% of the time we get either the right or center runway for landing. I briefed the approaches to both runways to cover myself. Twenty miles from the airport and at 10,000 ft we were were given a descent to 6000′ and a left turn to intercept the localizer for the left runway – of course.  I was half way through the turn when the captain reached to his left to retrieve his Jeppesen manual to get out the new approach plate. During his manipulations he inadvertently hit the autopilot disconnect button. We had chimes and bells galore and all the lights on the autopilot control panel extinguished. It’s really nice that the aircraft is so stable. A half dozen or so button pushes and we were back in business. The captain got the new approach and missed approach procedures programmed into the FMS and we re-accomplished all the required checklists for the new approach. We were then given a speed restriction of 160 knots and a descent to 5500′ as we approached the glidepath. I configured the aircraft for landing and waited for the approach clearance as the glideslope indicator appeared above us again. We were given a descent to 5000′ and still no clearance as we approached the glideslope from below for a third time. That little glideslope symbol came down to meet us and then buried itself on the bottom side of the indicator before we were given clearance for the approach, still restricted to 160 knots until 5-mile final.

This is a totally different way of being behind on a descent. The aircraft was already configured with all the drag it had available except the speedbrakes and we had a speed restriction. Luckily, the Airbus has no restriction on the use of the speedbrakes in the landing configuration, but the incremental amount of drag they would produce would not be enough to allow capturing the glidepath before the approach end of the runway. Our only option was to both extend the speedbrakes and increase our speed. The captain conveyed the message to the approach controller – increased speed or  vectors for another approach. We got the speed – less work for them. A 175 knot, idle-power dive managed to get us onto the glidepath by 1000′ agl with the speedbrakes still extended and our airspeed working its way down to the calculated approach speed. We were finally all stabilized by the required 500′ agl (VFR conditions) when I disconnected the autopilot and landed.  One turn off the runway another turn toward the concourse and two frequency changes and we were pulling into our arrival gate – twenty minutes ahead of schedule after a ten-hour flight.

The flying fun was over, then the commuting fun began. I won’t get into that other than to say that it was more of a zoo than the approach.  Now I have a week off before I start it all over again.

A Layover Lost

I mentioned the last time that I had been having problems sleeping in the European time zone. I guess I reached my limit of sleep deficit on that layover.The hallway alcove to my room. We reached our layover hotel and were checked into our rooms by about  10:30 in the morning. Some of us on the crew said that we would meet in the hotel lobby at 5 pm to go out in search of dinner. I eventually found my room – this is the look of the alcove where my room was located. I won’t go through all the comments I heard from the crew about the decorating motif of the hotel. There’s just not enough room in this column.

I partially unpacked, set my travel alarm for 4 pm, put the alarm clock next to the bed, crawled under the covers and fell asleep. I next woke up at 7:45 that night – never heard the alarm. (Yes, I checked it – the alarm was set and working.) I made some coffee, did a little computer work and headed downstairs for dinner. I was not familiar with the area around the hotel, it was a dark foggy night and I had seen a lot of tagging(graffiti) on the buildings in the area so I elected to just eat in the hotel restaurant. It was a very good meal, though expensive (even with our airline discount). Fifty-dollar meals quickly run through the per diem expense we are paid while out on trips.

That box checked, I went back to my room, checked email again and went back to bed. That produced another 5 hours of sleep and I started to feel human again. Our wake-up call came at 8 am for the flight back to JFK and we were soon in the bus headed back to the airport.

I apologized to the crew for missing the dinner date and found that those of the crew who had managed to wake up at the appointed time spent about an hour walking around the local area looking for a dinner spot. Most of the local restaurants (the hotel included) didn’t open for dinner until after 7 pm.

It was obvious during the drive to the airport that we were going to need a take-off alternate for the departure. The visibility was down at CAT III ILS minimums again. The Milan airport is located in a low area near a river. Go figure. It was a long, interesting taxi to the end of the runway – taxiway signs and holding point markers were slowly appearing out of the fog.

On departure we broke out of the low clouds at about 1500’ AGL into clear blue skies and a beautiful view of the Alps. It wasn’t long after that when I went back to bed again – sounds like that’s all I do. I happened to have the first break for the flight, so once safely on our way I headed for the pilot bunk for a couple of hours.

When I returned to the cockpit we were already over the Atlantic and making our way along our assigned North Atlantic Track (NAT). Luftansa A-330 on the North Atlantic Track system.The tracks are an organized system of routes (which change each day) controlled by Shanwick and Gander Oceanic Controllers. The NATs are like highways between the two continents with specific navigation points that require strict adherence to altitude and speed assignments. This Airbus A-330 was on our track 2000’ below us and apparently restricted to a slower speed than us. In listening to the airline chatter the winds at our altitudes were not different enough to allow us to pass them as quickly as we did. The only deviation to the assigned track that is allowed is what is called a Strategic Lateral Offset (Procedure) – yeah, referred to as a SLOP. We can offset laterally from the assigned track to avoid the wake turbulence generated by the aircraft in front of us. The offsets are always to the right and are restricted to 1 or 2 miles. That is why the Luftansa aircraft was off to our right – probably offset  a mile.

We made landfall again just north of Gander, Newfoundland and turned southwest toward New York.Maine's Mt. Katahdin in Baxter State Park. As we flew southwest we looked down and saw what looked like an old volcano in the middle of the state of Maine. It turns out that it is not volcanic, it just looks that way. Alpine glaciers carved out the depressions in the mountain, which is located in Baxter state Park. Mt Katahdin is the tallest mountain in Maine reaching 5270 feet about  sea level.

Now its almost time to head east again – this time to Amsterdam for the day/night. We’ll arrive early morning and leave the next morning. I expect I’ll sleep most of the day again.

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