Boeing 787-8: Basic math, cheating or misunderstanding certification requirements?

[thewinchester]

Interesting item in Plane Talking today, derived in part from a recent Flightglobal article from Farnborough comings and goings:

787 short cuts don’t add up for Jetstar
July 23, 2010 – 11:06 am, by Ben Sandilands

Boeing is saying strange things about the 787 from a passenger safety point of view as it evades a critically important test that might impede its rush to achieve certification by the end of the year.

This part of an article which has appeared in Flight International also quotes Boeing as saying the 787-8 has an evacuation limit of 250 passengers, which is likely to cause either hilarity or heart attacks in Jetstar, which is planning to take delivery from June 2012 of eight of them each fitted with 313 seats.
...
Of course, this could all be a huge misunderstanding, and the 787-8s will pass a physical passenger evacuation test of 313 passengers plus crew exiting through half the exits in 90 seconds OR Boeing will have to redesign the 787-8 for an evacuation limit of at least 313 passengers.

The former is more likely.

Some serious questions need to be asked however about Boeing’s short cutting really critical tests to get the 787 out of the factory door to its customers from the end of this year.

 

[rtyuiop]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

Yeah, I was intrigued by that one too - part of me finds it a bit too hard to believe, that they could possibly convince all the different aviation regulators around the world to accept evacuation tests which really come down to 'well, we *think* it'll work'.

We'll see. Now that it's started getting publicity I suspect Boeing will be running the test fairly soon...

Danny

 

[markis10]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

A little bit of information is dangerous, some facts:

Initial Certifications are not cast in stone, and often reflect the layout in terms of doors/seat types of the launch customer, not the maximum limits for the life of the aircraft production.
The 787 does not have a worse ratio of doors to seats than the 777 which is not limited to 250 pax, the BA incident was proof in a real life accident that the exits were sufficient.

Boeing have two years to work out evacs for JQ which are the first of the high density orders AFAIK, no big deal given the 777 experience.

Ben has been saying for a long time "the 787, is in diabolical strife", I think we know where he stands, I hate cut and paste "articles" that are just simply embellished before publication with additional FUD rather than showing a balanced view, for instance how does the design compare not only with the 777 but the CX A330 which recently also had a real life test?

Plane talking should be renamed FUD talking!

 

[rtyuiop]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

A little bit of information is dangerous, some facts:

Initial Certifications are not cast in stone, and often reflect the layout in terms of doors/seat types of the launch customer, not the maximum limits for the life of the aircraft production.
The 787 does not have a worse ratio of doors to seats than the 777 which is not limited to 250 pax, the BA incident was proof in a real life accident that the exits were sufficient.

Boeing have two years to work out evacs for JQ which are the first of th ehigh density orders AFAIK, no big deal given the 777 experience. What a load of FUD.

But the article suggests they're basing qualification on the 767, not the 777 - which seems rather obviously different to the dreamliner. To be fair, the article also does point out that certain parts of the evacuation system have to be demonstrated (doors, lights etc.).

The only thing which bugs me about it is that it makes me think Boeing is letting their delivery delay issues affect their testing. This might not be remotely rational (and I know nothing about the testing regimes of new airliners), but I can't help feel that if the 787 was on time they'd happily run the test!

Does anyone know how this compares to what Boeing did for the 777, or for the 737 NG?

Danny

 

[markis10]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

But the article suggests they're basing qualification on the 767, not the 777 - which seems rather obviously different to the dreamliner. To be fair, the article also does point out that certain parts of the evacuation system have to be demonstrated (doors, lights etc.).

Danny

You are missing the point, they are basing the cert on the 767 because the layout is the same for the initial aircraft to ANA etc, that is 230 seats, nearest closest match to the delivery aircraft. When they get to JQs config and the 787-9 you can bet the 777 will get referenced.

Lets use common sense, no aircraft is tested on the basis of two person exits, if the higher capacity 777 passes with a worse pax/door ratio then what is the issue, except for one of timing and ticks in the box.

 

[rtyuiop]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

I did say this probably wasn't very rational :mrgreen: .

I just find it unintuitive that a *completely* different type can be used as the basis for evacuation testing. I mean, the only things in common between the two are that they're long tubes with people inside (are the number of seats between each set of doors the same?)... While I can see the economy of testing the differences individually (testing doors, lights, announcement systems, etc.), I find it hard to believe it's not worth doing an all up test in case there's something that's been missed.

Again - not claiming it's rational, and I don't have the background to comment authoritatively, it just worries me... I'm still looking forward to my first 787 flight though!

Danny

 

[markis10]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

I mean, the only things in common between the two are that they're long tubes with people inside (are the number of seats between each set of doors the same?)... While I can see the economy of testing the differences individually (testing doors, lights, announcement systems, etc.), I find it hard to believe it's not worth doing an all up test in case there's something that's been missed.

Such tests are dangerous and often inconclusive, for instance do we allow for passengers holding up an evacuation because they wish to have an argument as was the case with US1493, or the fact not all doors will be available in a fire. Most evacuation tests have resulted in injury and sometimes death, they are not to be treated as things that are easy and cheap to do.

There are a lot of commonalities with the 767/777/787 and even A330 in general, the key things are the maximum time to get to an exit from any seat, and the rate at which passengers can disembark, that is doors to pax ratio. Just like buildings the key thing is how many exits and how long to get to the exit!

File:787sizecomp.svg - Wikipedia, the free encyclopedia

 

[docjames]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

or the fact not all doors will be available in a fire.

I thought there were some stipulations on how quickly pax can egress with 50% of exits (ie. one side) inoperative (eg. due to fire on one side of the a/c).

 

[markis10]

Re: Boeing 787-8: Basic math, cheating or misunderstanding certification requirements

I thought there were some stipulations on how quickly pax can egress with 50% of exits (ie. one side) inoperative (eg. due to fire on one side of the a/c).

There is that stipulation in 90 seconds with half disabled for certification overseas (its the one main cert test) but not operation, safety authorities are quickly realizing that there are other more important things in addition to that single test, to quote CASA:

The original certification demonstration proved that the aircraft type had sufficient egress areas and escape slides to enable evacuation of all occupants within the prescribed limits. Subsequent demonstrations must confirm that the cabin crew procedures, together with the cabin layout, permit replication of this result. For this reason the success criterion of evacuation within 90 seconds using 50% of the exits is not necessarily appropriate.Other criteria, which measure the effectiveness of crew procedures and training, assume greater importance. Such criteria include the time to open doors and emergency exits, together with compliance with individual crew procedures given in the Operations Manual.


The applicant should supply suitable evidence of the original certification demonstration, including the recorded times to open each exit. The criterion of time to evacuate a nominal passenger load assumes more importance when the cabin layout is different to that in the original demonstration or changes are made to the available exits.

Note the use of the phrase "sufficient escape areas and egress slides", logic suggests that if the 787 has less pax than a 777 and the some number then that requirement is satisfied. Note also the following from the same document which is part of the AOC Manual in relation to the initial issue of an AOC:

"The history of injury to participants in evacuation demonstrations, together with the likely cost of litigation, demands that the use of escape slides during emergency evacuation demonstrations be restricted to rare and unusual situations."