But flying the Airbus, I reach beyond my neighborhood and consult with Airbus representatives, a senior Airbus Check-airman, and miscellaneous Captains—my team.
I’m thankful to have the opportunity to consult with them on actual operations of various performance issues, and captain decision-making questions. Brainstorming before the event is always a good idea.
One of these issues is:
Overweight landing, and the need to perform an auto-land, or not.
The verdict is:
Airbus says, "there is no need to perform an auto-land with an overweight landing."
This is good to know. It would be a shame to not take advantage of a long runway because the ILS was down. A long runway with a heavy airplane is always the best.
Then, there is also the choice between low verses medium auto-brakes. I was reminded that the autobrake setting is a deceleration rate. The heavier the plane, the system will be using more brake pressure to stop at the same “decel” rate as when lighter. Noting since we have a higher approach speed, it takes more distance to slow down at the same rate.
The recommendation is: If you have enough runway, use low. Or even click the brakes off after touchdown doing the initial slowdown solely with reverse, so that the brake cooling time will be minimized and you can be on your way.”
One thing to keep in mind is for medical emergencies so you can drop off your passenger and get on your way quickly. Excellent advice.
Another question:
Does Airbus recommend managed speed for an overweight landing?
YES: Managed speed is recommended.
“There is a chance during the initial configuration that green dot speed may be higher than VFE for flaps 1 because of an over-weight condition. In this case, we recommend that the crew select speed VFE-5 kts (but not below VLS) to allow them to begin configuring. As the slats extend, VLS will reduce. Once that’s completed, the speed should be returned to managed speed.”
What Does Your Company Say?
Then there is also the question of deviating from your company procedures.
If you do something as a Captain, that is contradictory to your operations manual, but you view it as a better course of action, will you be violated? How far does your Captain authority go? If everything works out, no harm, no foul. But what if…
I think we all will do whatever it takes to save the plane if in imminent danger. But what if following the procedure is not unsafe, but in your view, a different course of action would be better. Can you do it? What will the FAA say? What will your company say? What will you say during your rug dance?
Share your thoughts, we would love to hear. And, I have the "FAA" answer to the will you be violated question. To be posted next week.
Enjoy the Journey!
XOX Karlene
From an outsider's pov, this sounds like a tough one. If this were to become a legal question (e.g. if there were a fatal crash involved), the airline would certainly come under lots of scrutiny, wouldn't it?
ReplyDeleteLinda, they would be under scrutiny. But then, Captains need to make the final decision. I don't think any decision should be based on "getting called on the carpet," but doing what is right. If you live to justify...that's a good thing.
DeleteTough question. Every company is different in that regard. I talked to our POI and he said if you don't follow the QRH procedure you could be violated. But that doesn't preclude you from doing what's necessary in a true emergency. In regards to the autobrakes, I have another Boeing and Airbus comparison thought. On the 767, the autobrakes use a deceleration rate(excluding the RTO position.) So we were told for brake cooling purposes if you use max reverse that the deceleration rate will remain the same because the brakes will automatically release pressure to compensate for what the reverse is doing. Does the Airbus work the same way?
ReplyDeleteDaniel, the brakes do work with a deceleration rate. Full reverse But... now that you mention it, is it like the Boeing? Not sure. The Boeing you could rotate the autobrakes to a higher setting while they're in use and increase the rate. (decreasing too)
DeleteSo, the difference between the low and medium. Low starts break application one second after spoiler application. And medium starts "at" spoiler application. The deceleration rate at Medium is higher than low, too. But yeah. It's all about the deceleration rate.
That is a good question. I remember in my SMS class doing this accountability chart; I can't find it now of course, but it goes through step by step to see if the pilot is accountable. It includes first and foremost normal operating procedures if it has been followed or not. Then it goes through this reasonable persons test, where they would see if a reasonable person in the same situation would do the same thing or not. It goes on a little bit more detail than that but I would think that it's fine.
ReplyDeleteIf he does it with the best intentions and safety of the aircraft then I think he shouldn't be faulted, so to speak. By he I meant the captain of course...whether he or she :)
Ramiel, that would be an interesting chart. I'm always under the contention that if you do the right thing with the best intentions you should be exempt. But the in the US negligence of the law isn't a get out of jail free card. So, the real answer lies in... did you know you were violating the rules. More next Tuesday on this.
DeleteI think that using the auto-brakes while performing an auto-landing would be disadvantageous, I mean, only if you have a long runway. If the auto-brake on a overweight plane uses the same deceleration rate on a normal weight plane, it would, probably, burn the tires, and, consequently, result on a high prejudice to the company to change the tires and all the burned components, plus the fuselage repair. So, in this case, I would only use the highly recommended procedure offered by the manufacturer. But If I have a significant short runway, performing a high speed approach, for an overweight plane, I would use the medium option at touchdown and, afterwards, while the aircraft slows down, I would change to the low option to avoid significant damage to the aircraft. And, of course, the engine reverse and the speed breakers always doing their job at the same time.
ReplyDeleteWell... There are a lot of scenarios to think on.
So I mentioned the ones that I think they were the main ones.
PS: I'm not a pilot, I still didn't have any classes, even PPL. I will start only in 2013. I don't know any of the procedures to follow. My opinion expressed may seem to be very illogical to some readers.
Thanks for your thoughts Alex. We always use autobrakes of some sort, on every landing. So, with the autoland it's a good idea. Deceleration rate is going to be varied with each weight. Also,we don't go from medium to low. Whatever the selection is... the next step is kicking them off and use manual brakes. The real question is "how much" you need. The performance charts have all the answers.
ReplyDeleteOoh... I get it! :D
DeleteThx Karlene! :D
How is the rate of acceleration calculated? More specifically is the rate calculated from one speed sensors or from a separate accelerometer just for the auto brakes? What happens to the auobrakes if which ever sensor the system uses to calculate the acceleration rate is broken?
ReplyDeleteRichard, excellent questions. The only part I can answer myself is that the autobrakes will not work if any part of the brake system is broken. For the rest... we might need an Airbus Engineer. Stay tuned, I'll see if I can find out for you.
DeleteRichard, we have an answer. The boss says it's the IRS. Specifically: "Well, at it's heart, what it really is is a couple of accelerometers (for linear accelerations) and the ring laser gyros for angular changes, and then a big vector-addition calculator to keep track of all the changes. So a deceleration rate (expressed as either Δgroundspeed/Δtime or a forward g-force) should really be a simple task for it."
DeleteHope that helps.
Thank you, I appreciate the time you took to look into finding the answer!
DeleteMy pleasure. It's good to have people!
DeleteDoes any one knows if the overweight landing QRH table provided with the overweight landing QRH check list is for a go around with one or two engines?
ReplyDeleteThe overweight landing charts are definitely for one "or" two engines. Imagine if you took off and lost an engine on departure. This is when you would have to return overweight. Yes... all overweight landing checklists are for various engine parameters. Thanks for the question!
Delete