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10th Apr 2019, 12:47
Replies: 5,127
Views: 10,297,629
Posted By LEOCh

Agreed with the rest of your post, but as a...

Agreed with the rest of your post, but as a counter-example to the statement above, consider a 737 NG loaded to it's absolute rear limit (36%MAC), and trimmed to fly at high but nonstalling AoA. It's...
2nd Apr 2019, 02:28
Replies: 908
Views: 947,744
Posted By LEOCh

Confusion about MCAS anti-stall

Thanks Ian. This confusion is very widespread in the current general (outside pprune) consensus of current MAX issues. Not only in the general media, but even in articles/content generated by...
20th Mar 2019, 07:51
Replies: 908
Views: 947,744
Posted By LEOCh

Thanks gums The idea of "pseudo-manual" mode...

Thanks gums

The idea of "pseudo-manual" mode raises an interesting point about how airliner automation has evolved somewhat ahead of certification philosophy. Besides the particular nacelle issue...
19th Mar 2019, 08:31
Replies: 908
Views: 947,744
Posted By LEOCh

Thanks, that makes a good deal of sense. I think...

Thanks, that makes a good deal of sense. I think if MCAS is updated with improved robustness of AoA sensing, and some sort of total stab authority limitation, it should be comparable to STS in risk....
19th Mar 2019, 06:12
Replies: 908
Views: 947,744
Posted By LEOCh

Not sure how single trim output can work for MCAS stabilisation

What information is available points to a MCAS software update that increases the robustness of the AoA input but restricts stab trim output to one cycle only.

However, I don't understand how a...
14th Mar 2019, 02:26
Replies: 5,127
Views: 10,297,629
Posted By LEOCh

Now that this is a huge international news story,...

Now that this is a huge international news story, it's interesting to see the developing outside media opinion/current consensus.

One very commonly expressed thread is that the probable JT610,...
13th Mar 2019, 14:19
Replies: 5,127
Views: 10,297,629
Posted By LEOCh

The AoA vanes on each side of the nose are not...

The AoA vanes on each side of the nose are not really two redundant sensors requiring a third to failsafe the system. This is because you don't necessarily expect them to agree during maneuvering,...
13th Mar 2019, 01:38
Replies: 5,127
Views: 10,297,629
Posted By LEOCh

To add a bit to this good explanation, Bjorn at...

To add a bit to this good explanation, Bjorn at Leeham news (who wrote a very good explanation of MCAS after Lionair) has a good followup that is available by googling "Bjorn's corner: Pitch...
11th Mar 2019, 06:55
Replies: 5,127
Views: 10,297,629
Posted By LEOCh

One thing that was I wondering after the Lionair...

One thing that was I wondering after the Lionair accident, was what are failure rates of the AoA vanes in general. Are they more or less reliable than the pitot-static systems they complement? This...
4th Dec 2018, 12:10
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

Hello Bernd, thanks for your reply I...

Hello Bernd, thanks for your reply



I would mostly agree but assert that static longitudinal stability in general requires the horizontal tail (stab+elevator) to be at lower AoA than the wing,...
4th Dec 2018, 09:00
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

I would have to respectfully disagree that the...

I would have to respectfully disagree that the MCAS is likely there to comply with FAA 25.175, along with the STS. Note the stick force requirement in that section is not at airspeed less than...
Forum: Tech Log
23rd Nov 2018, 22:52
Replies: 83
Views: 33,546
Posted By LEOCh

Thanks Mana for starting for a great STS thread,...

Thanks Mana for starting for a great STS thread, but also Vessbot and FCeng84 for some very high quality explanations of speed stability and augmentation.

I don't have much to add especially to...
18th Nov 2018, 09:10
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

This certainly makes sense, but I'm not sure that...

This certainly makes sense, but I'm not sure that two AoA vanes really constitute two sensors. Instead they are a special case as they are only semi-independant, (i.e expected to disagree somewhat...
16th Nov 2018, 05:46
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

The Leeham News article is quite informative of...

The Leeham News article is quite informative of why the MCAS is required on the MAX, and fills in some blanks. I originally thought heavier engines further forward should if anything bring COG...
14th Nov 2018, 06:22
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

Now that the new MCAS is firmly implicated, I...

Now that the new MCAS is firmly implicated, I wonder why it was implicated on the MAX. One possible reason was that it was considered to be required by transport airworthiness certification via...
11th Nov 2018, 01:57
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

Wow, thanks for posting. This appears to be the...

Wow, thanks for posting. This appears to be the missing puzzle piece, a new MAX system apparently unknown outside of Boeing which directly links AoA to the stab for improved stall protection (when...
9th Nov 2018, 22:46
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

Two questions I think are still unclear: ...

Two questions I think are still unclear:

Through what pathway did the faulty AoA sensor feed bad data to the trim stabiliser?
People are discussing the STS as a possibility, but AoA is not a...
4th Nov 2018, 02:07
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

Thanks Bru, am also operating on the assumption...

Thanks Bru, am also operating on the assumption that the maintenance logs are genuine and the faults on the previous flight point are likely factors on the accident flight.

The FEEL DIFF PRESS...
2nd Nov 2018, 01:33
Replies: 2,100
Views: 1,138,442
Posted By LEOCh

It is interesting to consider that a contributing...

It is interesting to consider that a contributing factor to this accident may have been the Boeing (vs Airbus) approach to introducing automation into the cockpit. Both the STS and elevator feel...
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