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737 Max/Poseidon

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737 Max/Poseidon

Old 24th Dec 2019, 10:22
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737 Max/Poseidon

Not looking for anything of restricted nature. How similar are the 737 Max and Poisidon in instrumentation and handling?
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Old 24th Dec 2019, 12:31
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" The Boeing P-8 Poseidon (formerly Multimission Maritime Aircraft) is a military aircraft developed and produced by Boeing Defense, Space & Security, modified from the 737-800ERX. "
https://en.wikipedia.org/wiki/Boeing_P-8_Poseidon
The P8 is not a Max.
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Old 24th Dec 2019, 18:12
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Still uses CFM's I believe, therefore no requirement for MCAS, therefore no certification problem.

Well, not on that count, anyway......................
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Old 24th Dec 2019, 19:22
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Taking that on a step to answer the question as put, the -800 (NG and P8) and -8 (MAX) are practically identical in instrumentation (= same type rating) but unfortunately rather different in handling at high angle of attack, hence the disastrously badly-implemented MCAS on the MAX. The handling differences are assumed to result from the larger and further-forward-mounted LEAP engines fitted to the MAX.

There is one little bit of the MAX story which bears upon all marks of 737 (including P8) which is the ability to recover from trim runaway using manual trim under heavy out-of-trim control loads. Those who’ve been following the MAX thread on Rumours & News may know that ‘back in the day’ the 737 manuals used to address this condition with a procedure known as the ‘roller-coaster manoeuvre’ but this was latterly deleted, presumably because it was considered unlikely to be needed and just a bit wacky. Classics and NGs (and P8s) have an automatic trim cutout switch which prevents full-deflection trim runaways. However this safety feature was removed as part of the MCAS implementation on the MAX with the results we’ve seen. It’ll be interesting to see what the federal inquiry says about the gradual loss of knowledge of the manual trim loading issue since its origins on the 707.

(Note 1: I am no 737 expert but have gained the above knowledge by following former Boeing flight control engineer Peter Lemme’s blog, which goes into detail on this topic and should be read in full by anyone with an interest in the MAX saga. His expertise is reflected in the fact that he was subpoenaed by the federal inquiry over the summer. An easier-to-read journalistic version is here. The Mentour Pilot video linked from the articles is worth a look to see the effect of mistrim.)

(Note 2: There is a suggestion out there that the manual trim wheels were reduced in size at the Classic-to-NG redesign to accommodate the NG’s larger FMC input unit; this would obviously reduce the leverage available to the pilots and raise certification questions (eg pilot strength requirements) but I haven’t seen this corroborated by sources as credible as Lemme. Another eagerly-awaited part of the federal inquiry report, perhaps? I wouldn’t get wrapped up about the P8 though; the thousands of NGs still flying hundreds of thousands of passengers daily are far more salient!)

Last edited by Easy Street; 24th Dec 2019 at 20:00.
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Old 24th Dec 2019, 21:31
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Easy Street: Ref the size of the trim wheels, I worked for an airline that had both -300 (classic) and -700 (NG) and we flew whichever was allocated for the route that day. It's been some 15 years, but I don't recall any difference in the size of the trim wheels.
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Old 24th Dec 2019, 23:11
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Originally Posted by isaneng View Post
Still uses CFM's I believe, therefore no requirement for MCAS, therefore no certification problem.

Well, not on that count, anyway......................

Not even the fan casing containment system that ...er didn't...
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Old 25th Dec 2019, 04:02
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And relax.....

Read the original question.... before slagging off Boeing.

Take a breath, those above (here we go...)

The P-8 (*Poseidon) has a Speed Trim System. Not MCAS.

The Speed Trim is bourne out of the fact that it has a 737-900 wing (with a few additions) and an -800 body.

Noting to do with MCAS. This is freely available on Google.
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Old 25th Dec 2019, 12:35
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[QUOTE=betty swallox;10647171]
And relax.....

Read the original question.... before slagging off Boeing.

Take a breath, those above (here we go...)

The P-8 (*Poseidon) has a Speed Trim System. Not MCAS.

The Speed Trim is bourne out of the fact that it has a 737-900 wing (with a few additions) and an -800 body.

Nothing to do with MCAS. This is freely available on Google or any open source. Some cracking info on the BBC News app.
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Old 25th Dec 2019, 22:22
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Betty. There are so many different issues it is very difficult to conflate the numerous issues.

Elevator authority, stab area, different manual wheel diameter/number of handles available to each pilot~~~ it just goes on and on.

Add in the management culture that has developed since the McD takeover......

...someone should be taking a looking glass to the certification of every 737 variant, civil OR NOT...
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Old 25th Dec 2019, 22:47
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Originally Posted by betty swallox View Post
And relax.....

Read the original question.... before slagging off Boeing.

Take a breath, those above (here we go...)

The P-8 (*Poseidon) has a Speed Trim System. Not MCAS.

The Speed Trim is bourne out of the fact that it has a 737-900 wing (with a few additions) and an -800 body.

Noting to do with MCAS. This is freely available on Google.
You might want to take your own advice: take a breath, here we go... read the responses properly, nobody said P8 has MCAS. In fact the responses are all crystal clear that it doesn’t. Why so defensive? The MAX accidents have brought about increased scrutiny of historic certification issues and it is possible to have a well-informed discussion about them given the amount of information which has been released into the public domain.
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Old 26th Dec 2019, 10:58
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I'm not so sure that MCAS wouldn't be prefectly acceptable to military users.
They'd know it was there, be trained in it's malfunctions and above all be sufficiently capable pilots trained in dealing with the trim excursions correctly if they occurred. As would civvy pilots...if they were correctly trained or capable.
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Old 26th Dec 2019, 11:11
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Originally Posted by meleagertoo View Post
I'm not so sure that MCAS wouldn't be prefectly acceptable to military users.
They'd know it was there, be trained in it's malfunctions and above all be sufficiently capable pilots trained in dealing with the trim excursions correctly if they occurred. As would civvy pilots...if they were correctly trained or capable.
Nice victim blaming
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Old 26th Dec 2019, 11:42
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Originally Posted by weemonkey View Post
Nice victim blaming
For his defense, he said he was "not sure", and then stated conjectures as to what he imagines would be the military response to a hypothetical MCAS that will never fly again.
Not exactly the same as affirming the usual "better (= US) pilots would have fared better" that experienced pilots unanimously dismissed.

Last edited by Fly Aiprt; 26th Dec 2019 at 13:39.
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Old 26th Dec 2019, 12:48
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The MCAS, as is, on a maritime reconnaissance aircraft frequently operating at very low level ?

Absolute madness.
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Old 26th Dec 2019, 13:58
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Originally Posted by RetiredBA/BY View Post
The MCAS, as is, on a maritime reconnaissance aircraft frequently operating at very low level ?

Absolute madness.
I think that pickle fork fatigue for an aircraft operating in a potential far harsher environment than normally encountered will be far under the microscope more than MCAS will need to be.

The pitch down issue with airflow disruption over AoA is currently managed on other in service platforms - its even been encountered by other nations during platform operation.
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Old 26th Dec 2019, 15:37
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Originally Posted by RetiredBA/BY View Post
The MCAS, as is, on a maritime reconnaissance aircraft frequently operating at very low level ?
Not necessarily, whilst the capability to operate at very low level by day and night is essential I think a relatively small proportion of the aircraft's time will be spent there. Indeed even on the MR1 and 2 we spent a fair amount of time at around 3000' and above. There are a whole list of things the P8 will not be doing like Stage 2 and Tapestry! I know they stopped ages ago but a lot of people who have never been involved with maritime air think that sort of thing will still happen. Neither do I think time will be spent doing endless radar or CTS homings to a moored buoy.

I do not know how the aircraft will be employed tactically but I do know it will not be Intermittent Radar with random tracks or Continuous All Round Scan (CARS) to deter SSGN that have to broach to fire.I am pretty sure however that a lot of airborne tactical time will be spent at medium level monitoring sensors; both active and passive. That doesn't mean we'll try the old ploy of blocking the gaps with a mountain of expended lofar buoys either, the P8 is going to have to be operated a lot smarter than that. Finally, you have to remember, the lower you go the less you see and hear and that can put you at a significant tactical disadvantage.

At present there is still a requirement to descend to low level to release ASW weapons. However when the goal of a standoff ASW weapon is realised; always assuming that the means to obtain an attack solution exists; then the requirement for low level diminishes further.

I'm not accusing RetiredBA/BY as he does raise a point, but some people tend to become fixated by low level and maritime operations (MOps). These days low level no longer has the primacy it once did.

However none of the above will prevent the RN tasking a MPA on DS with Airplan 4 Sectors 1 & 2 Circular 30-60....................you all know the rest! Ask a maritime crew member to explain that but be prepared to be told "Roger, wait out" . *

YS

* If you don’t know any maritime crew then ask oxenos as he’s even older than me!

Last edited by Yellow Sun; 26th Dec 2019 at 18:31.
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Old 26th Dec 2019, 19:55
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Originally Posted by VinRouge View Post

I think that pickle fork fatigue for an aircraft operating in a potential far harsher environment than normally encountered will be far under the microscope more than MCAS will need to be.

The pitch down issue with airflow disruption over AoA is currently managed on other in service platforms - its even been encountered by other nations during platform operation.
P8 has a different structure at the wing roots and ought not to have the same pickle forks ? It has a unique wing box design to accommodate the weapons bay.
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Old 26th Dec 2019, 21:04
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Originally Posted by AnglianAV8R View Post
P8 has a different structure at the wing roots and ought not to have the same pickle forks ? It has a unique wing box design to accommodate the weapons bay.

looks like a pretty robust design then! Not sure why people are getting their knickers in a twist about MCAS. With two accidents under their belt, Boeing and the FAA are going to be in the spotlight to ensure the design is squeaky clean.
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Old 26th Dec 2019, 22:45
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YS

When I joined "maritime" in 75, no *****er said anything about living in tents in the world's biggest sandpit, with a Airplan ****ing 4 nothing more than a misty-eyed memory.

Moral of the story...no **** has any idea what the P8 will end up doing for a living.

But I bet it will still be a blast for those lucky enough to crew it.
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Old 26th Dec 2019, 23:06
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Easy Street.

I am not being defensive.

read post #14.

I rest my case.

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