End of the Tunnel

Position: 100 miles west of Mylanta (KATL)
Altitude: 29,000 feet and descending; spoilers fully extended, idle thrust
Groundspeed: 563 mph (490 kts)
Souls on board: 189

My blood pressure is falling back to the normal range as the light at the end of the dark cumulonimbus tunnel comes into view. We are about clear (on the east side) of a line of thunderstorms spanning the southeastern quadrant of the Empire. The sun has just cracked the horizon. Hotlanta approach is accepting arrivals without holding... Life is good.

Before we picked our way through this line-up of Thor's children, the co-pilot told the lead flight attendant to batten down the hatches. I woke the passengers up, using my best imitation of the mythological captain's voice, and told them to take their seats and strap in tight. After I put the PA handset back in it's cradle, I remark to the co-pilot, "The passengers are probably freaking out back there because of AF447."

We are flying a new stretch Electric Jet (A321). She is long, lean and gorgeous. I did the pre-flight because the co-pilot, one of my all time favorites, claims to have (maybe) broken his little toe moving furniture for his girlfriend. Of course, I responded with, "yeah... Right!"

Well, we cannot have the co-pilot limping around the aircraft in view of the passengers, so, after attempting to make him feel guilty for his captain having to actually work before the flight, I put my earplugs in and descended the jetway stairs. Once I landed on the ramp, I was glad I had volunteered to pre-flight. The scene before me was visual overload; a new, pristine aircraft being loaded and fueled. She has no brake dust on her main landing gear wheels; they are perfectly white and untarnished. There are no ripples in her belly from hard landings, or streaks of hydraulic fluid that form between wash jobs. She is 40 feet longer, 40,000 pounds heavier, and carries 40 more passengers than the A320. In the world of aircraft, she falls into the beautiful category, or at least I think so...

Down the airways, approaching Memphis, we can see flashes with our eyeballs. They are popping like so many little strobe lights on the horizon. The A321's airborne digital weather radar (the latest and greatest) is showing good definition of the line. I truly wish some of my old Captain's could see this radar; they would be mighty impressed (only with the radar; definitely not the aircraft).

My instinct tells me to turn toward the south thirty degrees and look for a worm hole over Birmingham. I send a quick email to my dispatcher advising him on my plan in case he sees something from his end that I am missing. We have enough fuel to make a minor deviation from flight planned course line. The fingers of my right hand push a few buttons, and we are banking toward the south against the early morning star fields.

Here is where one of the A321's weaknesses becomes apparent, and that would be performance at altitude. The flight crew needs altitude in their tool box to deal with thunderstorms. It helps with visuals (eyeballs on the storm) and choosing a route in the clear, i.e., between storms. When the A321 is heavy, she cannot cruise much above 31,000 feet. Why is this? Well, it basically has the same wing and engines of the A320... Basically, not exactly. But close enough to be an impediment. This causes some of my buddies to have an extreme aversion toward the A321, bordering on visceral.

To me this is analogous to complaining about a beautiful woman not being able to cook. Who cares? Look at the total package. I will guarantee that the Captains (with a capital C) of yesteryear would have been very happy with 31,000 feet and 450 knots true airpeed when faced with a wall of weather in their radial-engine powered Douglas.

West of Birmingham, we can see the towering storms outlined against the pale pink light of the coming sunrise. They are big ones, full of water and veins of electricity, standing shoulder to shoulder between us and KATL. The co-pilot says something like, "This could get interesting."

I take the radar out of Fi-Fi's matrix for a few minutes and turn it into a manual storm prod, poking about in the weather looking for a worm hole to pass through to the other side. Air Traffic Control offers some info about a hole south of Birmingham that a few freighters are passing through. We can actually see that gap on the radar screen. It looks promising...

The flight attendants and pax are strapped in, Fi-Fi is slowed to turbulence penetration speed, and the weather radar is receiving good returns as we enter the tunnel between storms. I reach for the overhead panel and push two buttons to raise the forward ice shields (engine heat).

Two bright blue lights illuminate on the overhead panel. I tell the co-pilot, "Shields are up."

The clouds envelope us with turbulence and ice crystals hissing around the airframe. You can actually hear it. The forward Plexiglas windscreens begin to discharge tiny bolts of static electricity... They look like miniature lightning bolts. The real lightning bolts are on both sides of us; we cannot see them because we are in zero visibility conditions, but each bolt lights up our environment for a micro second with a strobe-light effect.

This is one of my least favorite job requirements; dealing with T-storms. Even though, I do it every spring and summer, year after year, it still makes me nervous. Not so much from fear of an accident, but fear of administrative trouble if we get struck by lightning or run into severe turbulence or hail.

Here is how it would probably go:

Board of inquiry- So, captain (with a little c), tell us again why you chose that particular route through the storms.

Me- Uh, well, I didn't have enough fuel to go around the south end... Uh, south of Baton Rouge.

Board of inquiry- Why did you not have enough fuel?

Me- Because you guys requested that captains stop carrying extra fuel over the flight plan fuel.

Board of inquiry- Well, captain, what about landing and taking on more fuel?

Me- Uh, yeah, I could have done that, I guess. But it costs $20,000 to land and take-off, plus it was night, unfamiliar airport, you know...

Board of inquiry- Yes, but the hail damage on the airframe is going to cost $3,000,000 to repair.

Me- (nervous fidgeting)

Board of inquiry- Do you think you need more training in the use of weather radar?

Me- No sir, I am qualified to teach weather radar classes.

Board of inquiry- OK, that will be all. You are excused for now. You will be hearing from the Chief Pilot's office within a week. For now, you are on administrative leave. Thank you captain.

It makes me sweat just thinking about it.

This airframe is long enough that the flight crew and the cabin crew can feel the flexing of the fuselage in turbulence. It is a bit like being on the end of a pole while something is shaking it. Hard to wordsmith the effect, but it is interesting, none the less. I have a habit of looking at the wing flexing, what little of it I can see, during weather penetrations. I cannot see the wing in this aircraft, only the red nav light on the wing tip. It is moving up and down, though. I guess that will have to do in a stretch Fi-Fi.

The indicated airspeed is varying plus and minus ten knots as we tip toe past the electric dragons on both sides of us. The airframe is flexing, twisting and thumping. I rotate the radar antenna upwards looking for tell tale signs of a hail column about to fall on us. Nothing... In a few more minutes , we will be out of this mess.

The darkness between lightning flashes is turning pink; an automatic stress reducer. Before I can finish thinking about it, we punch through the pink veil into the clear between two cloud layers. The sun is rising at the end of the tunnel. ATC gives us a lower altitude; KATL is close. My fingers push more buttons and The Electric Jet starts descending; I raise the wing spoilers to help her. We are high and fast on the vertical profile. As I tell the wife of my youth, "No problem, baby." In response, she usually rolls her eyes up and shakes her head.

The night is catching up with us. We are getting tired and looking forward to sleeping for a few hours. Tonight, we will do it again... Westbound.

Reminds me of lyrics from one of my favorite songs:

There is a feeling I get when I look to the west...
Stairway to Heaven, Led Zepplin

Life on the Line continues...

Fly-by-Wire

I was minding my own business, eating a light lunch in a Sacramento shopping mall and reading news on the mighty I-Phone. Imagine my shock to learn that Airbus Industries fly-by-wire flight controls may be dangerous! Holy Moly! Tell me it is not true! I read the article in full and was not surprised to learn that it was full of inaccuracies.

Anyway, I cannot abide such nonsense, so here we go... This will be a primer on the flight controls of the Electric Jet.

Note- for the most part, this blog does not go negative. This is what I call a Leisure Blog, i.e., something to do on overnights, nor does it get overly technical because I do not want to put the readers to sleep. Having said that...

Fi-Fi's flight controls

The Electric Jet utilizes fly-by-wire flight controls. That means that when the pilot, or the auto-pilot, sends a command to the flight surfaces (ailerons, elevator, stabilator, rudder, spoilers, flaps, slats), that command is an electrical impulse that activates a hydraulic servo or ram to move the control surface. There are numerous routes for the impulse to travel and there are three separate hydraulic systems to move the surfaces... Plenty of redundancy built into the flight control system. The fly-by-wire system is protected against outside electromagnetic pulses.

Here is where it gets tricky and throws some news reporters into a tizzy. When the pilot, or the auto-pilot, sends a command, it is evaluated by flight control computers. This is a very quick process; there is no perceptible lag from the time the pilot moves the stick, say to the left, and the left wing lowers. The reason the flight control computers take a look at the input is to attempt to keep the aircraft inside safe flight parameters. They try to keep the aircraft from what we call an upset. The protections will allow radical maneuvers, such as steep bank angles and high angles of attack if a need arises. But, if for some unknown reason, the aircraft is put into a dangerous attitude, Fi-Fi will attempt to help the pilot recover the aircraft with bank angle limits and overspeed or underspeed protection. It is a very good system and I do not feel limited by it in any way, shape, or form.

Also, if the aircraft gets into a low speed and low energy state, i.e., close to an aerodynamic stall, the flight computers will increase engine power and reduce angle of attack without pilot input. In fact, (pay attention: this is important) if all the protection values are operational, the aircraft cannot be stalled. That does not mean it cannot be crashed, though.

Example 1- Imagine you are cruising at 35,000 feet swapping flying stories with the co-pilot. The lead flight attendant rings and says your coffee is ready. The flight deck door is opened to hand over two cups of coffee and a screaming nut case dives into the cockpit, knocking the flight attendant into the center console, spilling hot coffee everywhere. The fight is on as the crew attempts to re-secure the flight deck. Someone's foot kicks the captain's joy stick, disconnecting the auto-pilot and sending Fi-Fi into an immediate left bank and nose down attitude. Anyone not seated with their belts fastened is in trouble. The flight envelope protections kick in and prevent the aircraft from rolling over on her back and keep the nose from pointing straight down. This gives the crew precious time to regain control of the aircraft and the flight deck.

Example 2- Imagine you are taking off at full gross weight, gear up, flaps retracting at about 2,000 feet above the ground. Your aircraft is accelerating when out of nowhere, a light aircraft is in your windscreen. Instinctively, you pull the stick back hard and to the right, trying to prevent a collision. The flight envelope protection system becomes your new best buddy in this situation. It will allow a steep bank angle and a nose high or nose low position, but will keep the aircraft from stalling, or rolling over during the frantic maneuver.

The flight envelope protection system has the ability to offer partial protection during equipment failure, such as a flight control computer. In cases of multiple failures, it is possible to have no protection, i.e., the flight controls revert to direct inputs to the control surfaces. In other words, the flight control protection always faults toward the pilot. A fault does not remove the pilot's ability to move the surface.


This wonderful system works in the background and is, for the most part, invisible. It cannot be normally turned on or off by the flight crew... Anyway, why would you want that?


Do not confuse the flight envelope protections with the navigation modes (lateral, vertical, and auto-thrust) that make The Electric jet such a wonder to fly. This aircraft is simply amazing in it's abilities to carry out the mission. Long time readers of this blog know that I refer to this as the Star Trek mode or as Smoke and Mirrors. All this magic can be turned off with a few button pushes causing the aircraft to revert back to the Super Cub mode... Poof! Stick, rudder, and manual thrust. Even in this basic mode, if all systems are in the green, the flight envelope protections will work.


Years ago, a major news outlet did a hit piece on the Airbus that was really out there in the ozone. To this day, I am still wondering why. Some of the things that were alleged were ridiculous. It was so bad, that Airbus had to create a response video that was distributed to training departments that operated their aircraft.

To prevent a misunderstanding here, I am not saying that the Electric Jet is perfect. I have thousands of hours in this baby and have flown it in horrendous conditions at the edges of the performance envelopes. I have seen several events that are head scratchers and have heard of others. Nor am I insinuating that Airbus aircraft are better than Boeing. As far as I am concerned, Boeing is the Holy Grail in aviation. I have thousands of hours in the 737-100/200/300 models, so I say that with some reverence.

OK, that is it for now. I hope this post was not too boring.

Life on the Line continues...

P.S. This comment just arrived from an Avionics engineer. It is written for the Line pilot, but since most readers of this blog are reasonably intelligent or you would not be reading it in the first place, you might find it interesting.

Hi Dave, As an Avionics Engineer of some 35 years spent mostly on corporate and commercial aircraft, I question how many people have seriously looked at the ADIRS computers in the A330/340. The ADS (Air Data System) and the IRS (Inertial Reference System) are completely seperate systems built into one box. The outputs of these two systems are used both seperately and summed to create a huge host of different data that is used by just about every other system on the aircraft. It is known by Airbus that the AOA (Angle of Attack) output from the ADIRU puts out erroneous data or "spikes" from time to time indicating up to 50deg nose up, and they have built certain algorithms into the PRIMS software of the primary flight control system (FCS) to filter these "spikes" out. However if 2 spikes are received that are within a certain time frame then the FCS will command a sharp nose down to recover from the stall indicated by the AOA. The ADS side of this system can be switched to another ADIRS system (3 onboard). The Airbus cure for the problem tells pilots to switch the IRS side instead. It is this error that caused the pilots of the Quantas A330 (VH-QPA) to continue to receive stall warnings and a host of other failures until they landed the aircraft an hour after the initial uncommanded nose down event. At high altitude the AOA measurement is sometimes the only indication that the aircraft is about to stall, or is already stalling, and hence the reason that the FCS will respond immediately and push the nose of the aircraft down when the AOA indicates a stall, In my opinion, only the software engineers at Airbuss will know what the FCS will do if the aircraft is in servere turbulance when an erroneous AOA output is acted on by the PRIMS. Further, the Yaw Damper System also receives data from the ADS and when in turbulance this system could be acting on erroneous data from the ADS and command large rudder movements that could cause the verticle fin to fail. Speculation in these circumstances is sometimes not a good thing, but sometimes it can highlight a weakness in an otherwise very robust system.
(name withheld)

MMMX

Position: Climbing out of MMMX (Mexico City)

Altitude: 28,500 and increasing...

Groundspeed: 500 mph (435 kts) and increasing...

Pax on board: 150 + 8 crew members

Equipment: A320 with V2500-A5 engines

We departed Mexico City ten minutes ahead of schedule with every seat full plus three extra crew members deadheading from a canceled flight. Mexico City is 7,300 feet above sea level, which in itself can be a performance problem. The airport is surrounded by high terrain, like in seriously high terrain, which is cause for concern. Our fuel load is less than I would like because of performance issues related with the density altitude and, of course, landing weight.

The Electric Jet is ascending into a wide river of wind, moving our direction at 100 knots plus, that begins at 28,000 feet and is allegedly 4,000 feet thick. The groundspeed is increasing rapidly. I can actually see the wind shearing off a cloud top abeam the left wing. That falls underneath the major cool category. We will ask ATC for an intermediate cruise altitude of 30,000 feet and use the free boost as long as it lasts.

Fi-Fi is nervous about the landing fuel, but she does not know (for sure) the route that we will be assigned closer to the arrival runway. I can look into her nav computers, an early version of HAL, and see that she is adding 60 (low altitude) miles to her calculation. My (admittedly feeble) mental fuel calculating loop says we will not fly those miles and thus will have legal reserve plus a little extra for any "uh-ohs."

Anyway, at the top of climb, wherever that might be related to our wind push, I will take a hard look at the fuel load. This will have to be managed with care because we do not want to arrive too heavy to land, nor do we want to get into a low fuel state. Too much paperwork required... Plus, I am getting too old for the carpet dance in the Chief Pilot's office. It hurts my left hip nowadays.

Life on the Line continues...

AF 447, continued...

As my British friend, Trevor says, "Hang about!" (translation: wait a minute) Gotta love those Brits!

The previous post on AF 447 has generated a lot of comments in a short period of time. Some of these comments need (in my opinion) to be addressed. Remember, generally speaking, that I do not go negative, I will keep this post within those parameters.

Airbus Industries does not make bad aircraft. They are robust and safe flying machines. Admittedly, they have a reputation for being complex. Of course, my Boeing buddies and I like to kid each other about our flying machines, but there are no major design flaws in the Airbus. The rumored quirkiness can usually be traced back to the pilot not understanding the system completely. Over the years, there have been a few changes in electrical design components and fuel system plumbing, but what aircraft has not? I have no complaints about Fi-Fi... She is a fine aircraft.

The AF 447 pilots did nothing wrong by taking off and flying toward Paris. Dealing with weather is part of our job. The crew cannot always fly around a line of storms, as (usually) there is not enough fuel to take major course line deviations. Sometimes, you have to pick your way through the weather with radar and eyeballs. Hopefully, the flight data boxes will be found and an answer to this tragedy will be forthcoming.

There is a report out that conflicting airspeed values were present at the time the A330 met it's demise. I have seen talking heads wondering if the pitot system was rendered inop by ice.

Also, they conjecture computer problems (which somehow the maintenance folks missed or were told by the evil CEO not to repair because of cost) may have generated airspeed instrument differences which caused the auto-pilot to disconnect.

Another report states that twelve other airliners flew through the same area without weather related problems. That leads the lay person to believe that it must be aircraft related. As any private pilot candidate is taught early on during training, there is no guarantee that a following aircraft can cross the same area of problematic weather successfully.

All of the data-link messages that this A330 broadcast before the end could have been caused by an encounter with a thunderstorm. The airspeed would flucuate wildly in severe turbulence causing the auto-pilot to disconnect, which in itself, is no big deal, because Fi-Fi handles very well with stick and rudder. Notice the could have in first sentence. That sounds just like a talking head!

The pitot system is well protected against icing. I am not sure, however, if it could be overwhelmed by super cooled water droplets present in thunderstorms. That possibility sounds incredible to me.

I still believe this accident was caused by an encounter with thunderstorm related high altitude weather. Every nasty weather condition that a pilot fears or should fear, is part of a thunderstorm and it is all contained in a small volume of atmosphere.

Life on the Line continues...

AF 447

Standby, please...

I just landed, finishing a four day. I need to sleep a couple of hours, then I will take a closer look at this disaster.

Later...

OK, now I feel better. The wife of my youth picked me up at the airport after flying all night, and then took me to my favorite breakfast joint. I spilled my coffee when I saw a breaking news report on the overhead TV about an A330 lost over the Atlantic. Say again, please...

I have been listening to the media talking heads and the aviation experts for about an hour since waking from my nap. Overall, I think the mainstream coverage is within the proverbial ball park on this one. I cannot believe I am saying this...

But, here are two things being reported with which I will disagree:

1. (Media says,"A bolt of lightning cannot, by itself, bring down a modern airliner.") A bolt of lightning could easily wreck an aircraft and cause a crash by itself. Yes, lightning strikes on aircraft occur everyday. I have been struck many times over my career. Usually, it is a non-event causing only minor damage or none at all. However, if an aircraft is in the vicinity of a very large thunderstorm, it could be struck by a super bolt of lightning wreaking total havoc with disastrous results.

2. (Media says,"Turbulence cannot, by itself, bring down a modern airliner.")Turbulence could easily wreck an aircraft and cause a crash by itself. Severe turbulence in the vicinity of a very large thunderstorm, or even a lesser one, has to be experienced to be believed. I have been inside thunderstorms several times in my career. It is unavoidable when you are a professional pilot. Anyone who disagrees with the previous sentence has not flown enough miles or has been very lucky. As a Line pilot, I go to great, even extreme lengths to stay out of thunderstorms for obvious reasons. Passengers pay me to deliver them safely to their loved ones.

A thunderstorm is a violent and scary entity. It has the power, and I mean real power, to easily rip the wings from an A330, or any other make or model of aircraft. No problem whatsoever.

On the automatic radio messages sent to Mother... Yep, Fi-Fi will send a message to the mainframe (think H.A.L.) when certain key malfunctions have occurred. It is a design feature of the Airbus Industries aircraft. Think you can hide a pesky malfunction from Mother so that you can do that last turn of the day and get home to Momma? You better be careful.

I will put forward two scenarios that may have happened to this jet:

First- Struck by a super bolt which fried the electronics causing depressurization, loss of electrical power and finally, a high altitude upset in IFR conditions (dark, turbulent, scary) leading to catastrophe.

Second- Encountered severe turbulence between or in thunderstorms. Airframe damage and/or failure leads to depressurization, loss of electrical power and finally, disaster.

Whatever happened, it was not pretty. The pax were terrified and the pilots were surely fighting until impact.

An A330 has crashed in the Atlantic... That fact is unbelievable.

Life on the Line continues...