Alaska 261

[Mitch Cronin]

Interesting beasts, these big Airbusses... What triggers the unlock of the tilt actuator? wheelspeed = less than ?? ... or time delay after making a prox switch, maybe?

As for your question Don... I'd have answered that a heavy or hard landing inspection would be needed anytime a pilot reported making one... or, certainly anytime a super-fancy aircraft recording system reported one... But heck, if you guys are gonna get out the calculators to see if it's needed, I'll wait 'til you push the = key and tell me.

But still, even if MCDU said all was well, I'd have a hard time answering "not required" if I'd read in the book that a pilot figured he'd dropped in on too hard or heavy. Having a good look can never hurt!

[boestar]

Going a little back in time I am looking at the 727 AMM and it says basically that the PILOT determines if a landing is hard or not.

If the hard landing aircraft is determined to be OVERWIEIGHT as well the overweight landing check replaces the HARD LANDING check.

This would lead me to believe that a heavy landing is worse that a hard landing.

Still it seems that the determination of a hard landing is left to the pilot to decide. Makes me wonder how many we have not seen in the past due to ego bruising.

B

[J.O.]

Good stuff as usual, Don. Thats the best explanation I've ever seen on the A330/A340 main gear bogie behaviour (that favourite of Airbus terms). For what it's worth, the best landing technique I've seen on the A330-300 is to check the sink rate at about 30 feet, and begin lowering the nose after aft bogie touchdown before selecting reverse. It seems to reduce the slamming effect of the front bogies. Now due to our lower limiting weights, our A330-300 may be landing at lower speeds than your typical 340 landing weight, so the need for reverse may be less critical in our case than in yours.

The figure of 16g you mentioned for the 621 accident, was that the load on initial touchdown after the spoiler deployment? If so, all I can say is, no wonder it turned out so badly.

Obviously, you've heard ET give some of his talks on the Airbus design philosophy and the man/machine interface. I'd love it if every pilot taking an initial course on the Airbus could hear him speak about 5 days before their first PPC. He has a beautiful way of making simple sense of the Airbus logic, which, contrary to what I first thought after a rather mediocre initial course in Toulouse several years ago, really is logical once you see it as he does. (By mediocre, I mean that I would have thought the builder would spend a little more time helping new pilots to understand the design philosophy or logic, which was still pretty new then).

Jeff

[Don Hudson]

Hi Jeff;

I heard ET talk about the Airbus philosophy at a Flight Safety conference in Pittsburgh (hosted by USAirways) and you're right...EVERY Airbus guy should hear this inspiring man speak about why they did things the way they did. His airplanes may be somewhat clinical but he is the warmest, most good-humoured gentleman one could ever meet.

The 330 doesn't seem to have quite the propensity to slam down that the 340 does and it may indeed have to do with the slightly lower speeds.

The remarkable thing about the 340/330 gear is that not only does it unlock on touchdown after providing some extra tail clearance, but it also pressurizes on liftoff and "pushes" the aircraft into the air, again affording an extra three feet or so of clearance for the tail. Its a solution to the problem of not having enough real-estate in the body wheel-well to store a longer main-gear strut. The oleo was shorter than what was needed, and Airbus solved the problem of obtaining tail clearance this way.

The technique you discuss is an excellent one in the view of many; it produces the most consistent de-rotations. Beating the bogies to the ground sometimes feels like one is leaping off the 30m board but it works, as long as one leaves the reverse alone until everybody on the main gear is on the runway.

A variation which worked wonders on the DC8 (and worked quite the opposite if one tried it on an L1011 !! ), was to begin the de-rotation with about 10 feet to go. But judging that under varying conditions can produce some interesting results. Sometimes it doesn't matter what one does and, like my daughter's horse, its mind is made up and nothing one does with the reins matters...

[Innuendo]

The sort of thread that on its own is worth the $25 for membership.

Interesting, now I have some idea why my landings were like my golf swing, not entirely predictable

I would hope that we could believe that cost alone is not the guiding factor in safety and maintenance. Otherwise you can expect to be running into that old chestnut "If you think safety costs money, wait 'til you have an accident"

[Don Hudson]

Innuendo;

Safety, as I know you know well, is an indeterminate, amorphous kind of notion where a corporation can pay a lot of money for "nothing" to happen. In a day/age where instrumentalism and blunt accountability prevail as the form of economic argument or discourse among managers and especially at the board and shareholder levels, the defence of an expensive "non-profit" department is extremely difficult, until, as you say, there's an accident. Shortsightedness in terms of "tomorrow's bottomline results" is not limited to politics.

Openly examining our industry's failures in relation to corporate decisions to fund "non-profit" internal enterprises isn't pointing fingers or whistling in the dark...its highlighting our industry's realities and how, over time and economic reality, we have come to terms with its unvarying realities: Ignore flight safety, and sooner or later, the price can be extremely high. That fact of course, extends to the regulator as is well understood.

These are statements of recognition of historical fact, not of discussable points of view in a somewhat academic argument. The key in all cases is, once again, balance. A perfectly "safe" airline doesn't fly at all.

Justification of safety programs arrives, in this instrumental (digital) age, through hard data, not opinion. That is one reason for the extensive proliferation of "data-driven" programs from those folks whose primary fight is flight safety, and its a good argument because data can effectively drive programs with rational, logical justifications, even in a bottom-line driven discourse.

I truly believe that cost alone is not a singular driving factor in this aspect of our business. Reluctance may accompany decisions, but, frankly, the decisions are there nevertheless. Like any major carrier, the effective and knowledgable management and balance of risk is crucial to an economic as well as an operational success. Finding that balance means active listening, approprate action and caring insight into those more "enduring" regions of this industry.

[IFG]

Here's where the inherent disadvantages of this format arise - the thread has forked in two directions; so .... to start anew or break the continuity .... staying at the same locale, Re:

I understand how enterprises like Aeroplan and Jazz can (and must) operate "like a real profit-focused business", but I don't really understand how "the maintenance group" can operate under the pressures of being "held accountable" for "big results" by being run as "true, profit-focused businesses" .... [and] .... I don't see how an organization within an organization can "profit" from doing "business" inter-departmentally, even if strictly separate budgets are maintained. How does the "profit" show up on the larger organization's year-end reports? "Who's" profit is it? What is the meaning of "profit" when one department is "charged" by another and it shows up as "profit"? ....

Hi, Don (& Mitch, de-icer etc) - words' meanings are shaded by context, and in this case, "profit" for a division can be a means to an end, or a measuring stick, of the contribution to the ultimate results of the enterprise. In this instance, the wisdom and necessity of good maintenance would hardly be questioned, but the efficiency attending it is a legitimate concern. A profit-centred accounting enables monitoring and comparison, at least in the crudest sense with outside providers, to assure that efficiency. There is a tendency to assume that "breaking even" is sufficient, but that ignores the initial and ongoing investments which might be more gainfully put to use elsewhere, with selling off a subsidiary being an option to achieve that.

As an analogy, years ago I did my own car and home maintenance. The equivalent time spent at my chosen pursuits had lower "yield", thus my own time was a lower cost than "out-scourcing". Happily the reverse is true now, I'm "more productive" at my own line of work, so it's "profitable" to my pocketbook to pay to have the other stuff done .... not even touching the question of work quality

Assuming an equal quality of work is available out there (and assuming otherwise gratuitously insults the professionals and tradesmen at other shops), IF you can fly airplanes profitably, but not maintain them more efficiently than outside contracting, then an airline is farther ahead investing in the deployment of more airframes, than in setting up more infrastructure. But wouldn't you think a top-flight, sought-out maintenance organization can justify itself, and thus have no fear of showing that on a balance sheet?

And Re:

What constitutes a heavy, or hard landing? .... The airframe is certified for 2.5g's in the air, 2.0 if the slats/flaps are out, but I have yet to find information on the above question .... A landing which is generally felt to be 'firm' occurs around 1.5g's, and of course the spike is very quick. The 621 accident in 1972 recorded 16g's in the cabin and it was mathematically determined that the wings/engine mounts experienced, I believe, over 20g's.

I'd be interested to know how the 621 g-loads were arrived at, e.g. why the wing & engines would have higher loads - maybe some unfortunate harmonics in wing-bending during the "impact"?

As to the general "what constitutes ...", I've heard 700, even 1000 ft/min bandied around, and was once told that the A/C had to sustain being dropped free from 3 or 4 feet , but not seen anything substantiated. Idle speculation with a little physics and 'rithmetic:

If the oleos can absorb the ROD without hitting their stops & transmitting a shockload to the airframe, that ought not to be condisered a "hard" landing. Most transport category A/C have a max around 2g's in the landing config. Calculating a rate of descent reduced to 0 over the length of the oleo extention would probably provide some loose guidance. I don't know what full extension is, but I'd think 12" would be very conservative. 2 g's being 64 ft/sec2, over a 12" extension, allows a ROD of @ 700 ft/min, more if the oleo extends longer, or less if .... 1000 ft/min would need about 24" of oleo at 2 g's. Interestingly, vis-a-vis the drop-the-aircraft theory, 700 would be the aprox ROD in around 2 ft of freefall, 1000 in 4 ft

You're starting a few good discussions here, Don - hope that as many see and/or partake under the new protocols, 'cuz, as Chilliwac used to sing .... without the audience there ain't no show ....

Cheers, IFG