MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
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The fact that the AOA sensor uses set screws instead of indexing shows to me that it was never considered to be a part critical to safety. If there was one moment when Boeing "jumped the shark" it was when they promoted a part whose failure was rather innocuous to one that had authority over a large flight control surface. I think we might be going somewhat down the same road with automobiles, the parking radar that beeps when you get too close to a wall can now slam on the brakes at 70mph. One hopes that automotive engineers are more attentive to Murphy's law than aerospace engineers.
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The fact that the AOA sensor uses set screws instead of indexing shows to me that it was never considered to be a part critical to safety. If there was one moment when Boeing "jumped the shark" it was when they promoted a part whose failure was rather innocuous to one that had authority over a large flight control surface. I think we might be going somewhat down the same road with automobiles, the parking radar that beeps when you get too close to a wall can now slam on the brakes at 70mph. One hopes that automotive engineers are more attentive to Murphy's law than aerospace engineers.
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$300,000 Pilot Jobs Drying Up in China After Boeing Grounding
From Bloomberg, yesterday:
Expatriate pilots flying Boeing Co.’s most popular plane for Chinese airlines used to be able to take their pick from dozens of jobs paying $300,000 plus perks thanks to a shortage of experienced aviators there. The grounding of the 737 Max has changed that.
Chinese carriers have largely stopped hiring foreign pilots for Boeing’s main narrow-bodied jet, nine months after two crashes led to the grounding of the best-selling 737 Max, according to recruitment agencies. Airlines in China’s booming aviation market had been among the most enthusiastic buyers of the plane, accounting for 20% of a global fleet that now sits idle.
Chinese airlines still pay above-market wages but the lengthy grounding has hit a swath of roles paying multiple times the median salary of a commercial pilot in the U.S. With no clear time-line for the Max’s reinstatement after two lethal crashes, demand for expat pilots of any 737 variant in China has slowed to a trickle. Only a handful of the country’s airlines are recruiting for such jobs now.
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Chinese carriers have largely stopped hiring foreign pilots for Boeing’s main narrow-bodied jet, nine months after two crashes led to the grounding of the best-selling 737 Max, according to recruitment agencies. Airlines in China’s booming aviation market had been among the most enthusiastic buyers of the plane, accounting for 20% of a global fleet that now sits idle.
Chinese airlines still pay above-market wages but the lengthy grounding has hit a swath of roles paying multiple times the median salary of a commercial pilot in the U.S. With no clear time-line for the Max’s reinstatement after two lethal crashes, demand for expat pilots of any 737 variant in China has slowed to a trickle. Only a handful of the country’s airlines are recruiting for such jobs now.
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The fact that the AOA sensor uses set screws instead of indexing shows to me that it was never considered to be a part critical to safety. If there was one moment when Boeing "jumped the shark" it was when they promoted a part whose failure was rather innocuous to one that had authority over a large flight control surface. I think we might be going somewhat down the same road with automobiles, the parking radar that beeps when you get too close to a wall can now slam on the brakes at 70mph. One hopes that automotive engineers are more attentive to Murphy's law than aerospace engineers.
While it might be the case that the resolver connection could slip, there isn't any resistance except to angular rate of the vane accelerating the core of the resolver to create loads passing through those set screws. It they were completely loose, the resolver would have no torque to turn it and it would report an unchanging value. Resolvers are small and very easy to turn; those loads are small.
In the case of Lion Air, it's possible the inaccurate resolver was indexed 20 degrees off from where it should have been; it remained exactly that amount through both flights. ET302 saw the resolver reading in accordance with aircraft acceleration just like a plumb bob would follow.
One final thing - the gear attachment is not adjusted to change the calibration of the sensor, the body of the resolver is turned to do that after a rough alignment according to the gear teeth, so the gear could be an interference fit on the resolver shaft and the vane shaft with the setscrew being a belt for suspenders approach. The resolver body is indexed with three cleats.
Last edited by MechEngr; 15th Dec 2019 at 18:44.
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While it might be the case that the resolver connection could slip, there isn't any resistance except to angular rate of the vane accelerating the core of the resolver to create loads passing through those set screws. It they were completely loose, the resolver would have no torque to turn it and it would report an unchanging value. Resolvers are small and very easy to turn; those loads are small.
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It looks to me that the setscrews index the resolver to the balanced assembly of the vane and the counterweight and that the counterweight is indexed to the vane with a flat on the side of the vane shaft. One can see the flat-bottomed groove in the counterweight that receives the vane shaft. Maybe there was a failure of one or more of the screws that hold the item 45, shaft retainer (?), in place. If so, the resolver would still be attached and the vane would mostly follow the oncoming wind. It seems unlikely as the plane was not exposed to a high g load at the time; I would expect it to fail that way on a hard landing or bumping down the runway during take-off.
While it might be the case that the resolver connection could slip, there isn't any resistance except to angular rate of the vane accelerating the core of the resolver to create loads passing through those set screws. It they were completely loose, the resolver would have no torque to turn it and it would report an unchanging value. Resolvers are small and very easy to turn; those loads are small.
In the case of Lion Air, it's possible the inaccurate resolver was indexed 20 degrees off from where it should have been; it remained exactly that amount through both flights. ET302 saw the resolver reading in accordance with aircraft acceleration just like a plumb bob would follow.
One final thing - the gear attachment is not adjusted to change the calibration of the sensor, the body of the resolver is turned to do that after a rough alignment according to the gear teeth, so the gear could be an interference fit on the resolver shaft and the vane shaft with the setscrew being a belt for suspenders approach. The resolver body is indexed with three cleats.
While it might be the case that the resolver connection could slip, there isn't any resistance except to angular rate of the vane accelerating the core of the resolver to create loads passing through those set screws. It they were completely loose, the resolver would have no torque to turn it and it would report an unchanging value. Resolvers are small and very easy to turn; those loads are small.
In the case of Lion Air, it's possible the inaccurate resolver was indexed 20 degrees off from where it should have been; it remained exactly that amount through both flights. ET302 saw the resolver reading in accordance with aircraft acceleration just like a plumb bob would follow.
One final thing - the gear attachment is not adjusted to change the calibration of the sensor, the body of the resolver is turned to do that after a rough alignment according to the gear teeth, so the gear could be an interference fit on the resolver shaft and the vane shaft with the setscrew being a belt for suspenders approach. The resolver body is indexed with three cleats.
https://www.satcom.guru/2019/03/aoa-...-fix.html#more
IMHO- the use of set screw(s) for such an instrument is or should be verboten
D shaped shaft with snapon keeper, splined shaft with d ring keeper or similar should be used for all such assemblies especially counterweight to gear shaft and gear shaft to resolver and arranged that any broken part vane gives a nose down ? result with mechanical limits as to movement or resolver output. Wilbur and orville may have used a few setscrews on their flyer- but that was then ...
Of course if you want to adjust your lionel railroad and engine parts, or your kids toys, even then set screws are now doubtful, since they may be swallowed. Maybe to adjust your clock or doorbell chimes is OK ?
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The recent comments about MCAS reinforce the point that it is very difficult to design a complex system that is safe, effective and reliable, and operates within the limitations of the human-machine interface.
From an entirely different perspective, this
reminds me of the (apocryphal) story of the monkey trap. Once the hand has gripped the food reward, the size of the fist is too large to withdraw from the trap.
MCAS software seems like a clever fix, but may actually be a trap. All kinds of contortions and wriggling, do not solve the underlying physical problem,.
Letting go of the 'easy' software fix may seem painful, but it might be worse to be trapped in a never-ending tug-of-war between physics, regulations and safety.
From an entirely different perspective, this
reminds me of the (apocryphal) story of the monkey trap. Once the hand has gripped the food reward, the size of the fist is too large to withdraw from the trap.
MCAS software seems like a clever fix, but may actually be a trap. All kinds of contortions and wriggling, do not solve the underlying physical problem,.
Letting go of the 'easy' software fix may seem painful, but it might be worse to be trapped in a never-ending tug-of-war between physics, regulations and safety.
Yes, a complicated diagnostics can be made to detect the disaster preconditions, but... . Far more straight forward would be to add actuator somewhere between stick and elevator to generate the right stick force (system that could be deactivated in a moment) if the problem were really the stick forces. Of course, the situation might be more complicated that announced publicly.
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Yes, a complicated diagnostics can be made to detect the disaster preconditions, but... . Far more straight forward would be to add actuator somewhere between stick and elevator to generate the right stick force (system that could be deactivated in a moment) if the problem were really the stick forces. Of course, the situation might be more complicated that announced publicly.
It is hard to believe one of the roles of MCAS was "linearize" the instantaeous stick force with a coarse one-size-fits-all multiple shot action of a powerful but slow moving control.
Most of us have suggested some sort of stick nudger in the past months would have been more appropriate.
There might be more to it than announced, be it anomalous aircraft behaviour, lack of proper elevator authority, or just plain lack of engineering resources...
Psychophysiological entity
I would have thought MCAS, as a concept, was an eloquent answer to a tedious flight-test finding, given that you allowed any automated system to control the H Stabilizer. The prime issue with MCAS was its uncensored authority over that ultimately powerful surface.
There shouldn't have been a multiple shot action but a smooth adjustment of stick load. A stick nudger is totally different and not at all what was required to solve the aerodynamic problem.
The two vane failures were seemingly a bizarre coincidence since there seems little doubt they were quite disparate mechanical issues. Re the ET failure, I note on the diagram the shaft from the vane has quite a small diameter and it seems likely that if it failed, the vane would be free to extract itself and fly/flutter/tumble chaotically to the left side of the centreline. I wouldn't be surprised to find it 50 metres from that line.
There shouldn't have been a multiple shot action but a smooth adjustment of stick load. A stick nudger is totally different and not at all what was required to solve the aerodynamic problem.
The two vane failures were seemingly a bizarre coincidence since there seems little doubt they were quite disparate mechanical issues. Re the ET failure, I note on the diagram the shaft from the vane has quite a small diameter and it seems likely that if it failed, the vane would be free to extract itself and fly/flutter/tumble chaotically to the left side of the centreline. I wouldn't be surprised to find it 50 metres from that line.
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I think most of us are still trying to figure out how any of this makes good engineering sense -- even if the system design hadn't been so truly awful.
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Difficult to imagine how to linearize the forces in a variable elevator movement (quick, slow, long, short, etc.), with a stabilizer that moves always the same value at the same rate.
Looks as if they only considered steady state.
Really puzzling.
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AEROSPACE & DEFENSE
Spencer Kimball
@SPENCEKIMBALL
https://www.cnbc.com/2019/12/15/boei...j-reports.html
Boeing reportedly nears decision on cutting or halting 737 Max production
PUBLISHED SUN, DEC 15 20195:36 PM ESTUPDATED 24 MIN AGOSpencer Kimball
@SPENCEKIMBALL
https://www.cnbc.com/2019/12/15/boei...j-reports.html
Well . . . but what, exactly, is the aerodynamic problem? We've been told that it's a pitch-up tendency in some corners of the envelope and that MCAS was required to create linear stick forces to help keep the airplane out of those corners. OK, but using the H-stab for that job is pretty radical. Also, as Grebe and others have pointed out, stab trimming is inherently slower than the elevator movement controlled by the yoke, so it seems like an odd choice for that reason.
I think most of us are still trying to figure out how any of this makes good engineering sense -- even if the system design hadn't been so truly awful.
I think most of us are still trying to figure out how any of this makes good engineering sense -- even if the system design hadn't been so truly awful.
It looks to me that the aerodynamic problem is that the engine nacelles produce non-linear lift at high AoA. The only ways to eliminate that would either to make the nacelles produce lift that is linear with AoA, a big trick for a round can or to put the Cp of the engine nacelle coincident with the Cp of the remainder of the plane - the latter is quite the trick as the Cp of the plane moves with AoA.
MCAS makes a lot of sense. It's inexpensive (should have been anyway) and does not generate drag and fuel costs under normal flight the way that adding a larger stabilizer and larger elevators and adding structure to the fuselage for their higher loads and heavier gear to handle the heavier load and bigger fuel tanks to make the range which add more weight for fuel and more weight for the tanks and more weight in the wings to carry that weight and more weight in the landing gear - and so on.
The AoA system that feeds it lies and also lies to the stall warning and stick shaker does not make sense.
Suggest take time to read this link - which includes pics and diagrams
https://www.satcom.guru/2019/03/aoa-...-fix.html#more
IMHO- the use of set screw(s) for such an instrument is or should be verboten
D shaped shaft with snapon keeper, splined shaft with d ring keeper or similar should be used for all such assemblies especially counterweight to gear shaft and gear shaft to resolver and arranged that any broken part vane gives a nose down ? result with mechanical limits as to movement or resolver output. Wilbur and orville may have used a few setscrews on their flyer- but that was then ...
Of course if you want to adjust your lionel railroad and engine parts, or your kids toys, even then set screws are now doubtful, since they may be swallowed. Maybe to adjust your clock or doorbell chimes is OK ?
https://www.satcom.guru/2019/03/aoa-...-fix.html#more
IMHO- the use of set screw(s) for such an instrument is or should be verboten
D shaped shaft with snapon keeper, splined shaft with d ring keeper or similar should be used for all such assemblies especially counterweight to gear shaft and gear shaft to resolver and arranged that any broken part vane gives a nose down ? result with mechanical limits as to movement or resolver output. Wilbur and orville may have used a few setscrews on their flyer- but that was then ...
Of course if you want to adjust your lionel railroad and engine parts, or your kids toys, even then set screws are now doubtful, since they may be swallowed. Maybe to adjust your clock or doorbell chimes is OK ?
How would the AoA sensor assembly detect it had a broken part in order to generate a "nose down result"?
Last edited by MechEngr; 16th Dec 2019 at 03:14.
Take a look at the Satcom Guru post jimjim1 cited and at the AAIB bulletin linked there.
The AAIB bulletin also notes that of two AoA sensors one was not assembled correctly, as opposed to coming loose, and the other had a persistent electrical problem blamed on a tiny particle in one of the pick ups that gave a glitch at a certain orientation. There's something to be said for idiot proofing assemblies, but it seems like there is no consistent history of AoA sensors with internal parts coming loose. More concerning, from the report, is they had placed a previously removed electrically deficient sensor back on the plane without finding the original defect it was removed for. I'm surprised they did not send it back to the manufacturer for diagnosis, but I'm not surprised they did not understand how to diagnose it correctly. A continuity meter and a quick turn is not sufficient.
The solution, if it was a problem, would be a drop of shaft-locking material. Henkel makes several grades. It would not get an item number on a diagram, but be included in the same instructions as define the acceptable required torque.
What does a 737 Max sensor look like inside, years later?
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Seattle Times
https://www.seattletimes.com/busines...risis-extends/
Shutdown likely at Boeing Renton as 737 MAX crisis extends
Dec. 15, 2019 at 4:29 pm Updated Dec. 15, 2019 at 6:59 pm
By Dominic Gates
Seattle Times aerospace reporter
The Boeing board is weighing a proposal from top management to temporarily shut down 737 production in Renton, with an announcement likely either after the financial markets close Monday or early Tuesday, according to a person close to the decision makers, who are meeting Sunday and Monday in Chicago.
It’s likely Boeing will stop 737 MAX production this week or next and keep the assembly lines closed until the Federal Aviation Administration (FAA) clears the jet to return to commercial service, which is currently expected around mid-February or early March, the person said.
“It depends on the return to service. How long is that going to take? Is it 60 days? Probably,” the person said. “You can only build them for so long without delivering.”
Ahead of the Christmas break, the imminent shutdown is tough news for Boeing’s Renton workforce, though not unexpected nine months into the grounding of the MAX and shortly after government officials telegraphed that it’s likely to extend to almost a year.
The person close to the discussions said Boeing intends to do what it can to have “as little impact on employees as possible.” He said the company will transfer some of the roughly 12,000 people who work in Renton to other production facilities in the region, including the Auburn parts plant and the Everett widebody jet plant.
However, the other facilities don’t have the capacity to absorb all of the Renton workers, and a substantial number of furloughs are likely, though perhaps beginning only after the normal holiday break for Christmas and New Year’s, which typically runs from Christmas Eve through New Year’s Day.
Last week, FAA Administrator Steve Dickson pushed out approval for the MAX to fly passengers again into next year, and then told Boeing CEO Dennis Muilenburg in a meeting in Washington, D.C., to dial down public statements suggesting a return to service was imminent.
Privately, officials identified mid-February as the new target for FAA clearance, assuming no further slips in the schedule.
The safety agency has not yet completed its review of the software fix Boeing developed for the new flight control system that activated erroneously on the two MAX crash flights and repeatedly forced the down the nose of each of the jets.
In addition, both the FAA and foreign regulators are assessing how pilots will handle the changes to the flight control systems and what training will be required before a pilot can fly the jet with passengers aboard.
Muilenburg had said in October that a production stoppage or a further cut in the production rate could be necessary if the FAA approval process for a return to service extended into 2020.
More than 800 MAX aircraft are now grounded worldwide. About 500 of those built since the grounding are parked around the Seattle area and at Moses Lake in Eastern Washington, undeliverable for now.
It’s unclear if Boeing will continue production of the 737-based Navy anti-submarine plane, the P-8, which is built on a separate assembly line in Renton and based on a model preceding the MAX. However, that is a low-production line, rolling out just one or two planes a month.
The MAX had been produced at a rate of 52 jets per month until the plane was grounded, and since then was cut back to 42 jets per month.
The impact of a MAX shutdown would ripple out through Boeing’s 737 supply chain and would idle aerospace workers across the nation and internationally.
Among the most affected suppliers is Spirit AeroSystems of Wichita, Kansas, which assembles the MAX fuselages and sends them to Renton by train.
Once production is slowed or stopped, it’s not easy to ramp up again. For that reason, since the grounding in March, Spirit has continued to maintain the pregrounding build rate of 52 fuselages a month even though Boeing was accepting only 42 per month.
That has meant fuselages stacking up in Wichita even as completed jets stacked up in Washington state. A complete halt in Renton will likely force a halt in Wichita.
Another big supplier is CFM International, a joint venture between GE and Safran of France, which builds the jet’s new LEAP engines at facilities around the U.S.
Smaller suppliers could potentially be even more affected.
In the currently booming U.S. job market, a small supplier that has to lay off workers for as long as 60 days is likely to lose those employees as they find work elsewhere. That means hiring and training new people in order to bring production back up.
A shutdown would also amplify the financial impact of the grounding on Boeing.
While production is stopped, many fixed overhead costs continue. Because Boeing’s costs during any shutdown period will be spread over many fewer aircraft than previously projected, it’s likely the company would have to announce another big accounting write-off when it reports its quarterly earnings in January.
Through October, Boeing had already projected $2.7 billion in extra costs due to the previous 20% production cut, in addition to a $5.6 billion write-off to cover compensation to suppliers and customers.
Even though a shutdown was somewhat anticipated, the stock may take a hit on Monday.
There are also broader impacts: Boeing is the country’s largest exporter, and the inability to deliver 737 MAXs to overseas airlines has already widened the 2019 trade deficit. As the U.S. heads into a presidential election year, job losses from a production shutdown will heighten political concern and possibly add to pressure on the FAA to speed up its review of the MAX.
The current discussions around weighing a Renton shutdown were first reported Sunday by the Wall Street Journal.
Boeing had no comment Sunday, and simply repeated a statement sent out Thursday that “we will continue to assess production decisions based on the timing and conditions of return to service.”
Dominic Gates: 206-464-2963 or [email protected]; on Twitter: @dominicgates.
Dec. 15, 2019 at 4:29 pm Updated Dec. 15, 2019 at 6:59 pm
By Dominic Gates
Seattle Times aerospace reporter
The Boeing board is weighing a proposal from top management to temporarily shut down 737 production in Renton, with an announcement likely either after the financial markets close Monday or early Tuesday, according to a person close to the decision makers, who are meeting Sunday and Monday in Chicago.
It’s likely Boeing will stop 737 MAX production this week or next and keep the assembly lines closed until the Federal Aviation Administration (FAA) clears the jet to return to commercial service, which is currently expected around mid-February or early March, the person said.
“It depends on the return to service. How long is that going to take? Is it 60 days? Probably,” the person said. “You can only build them for so long without delivering.”
Ahead of the Christmas break, the imminent shutdown is tough news for Boeing’s Renton workforce, though not unexpected nine months into the grounding of the MAX and shortly after government officials telegraphed that it’s likely to extend to almost a year.
The person close to the discussions said Boeing intends to do what it can to have “as little impact on employees as possible.” He said the company will transfer some of the roughly 12,000 people who work in Renton to other production facilities in the region, including the Auburn parts plant and the Everett widebody jet plant.
However, the other facilities don’t have the capacity to absorb all of the Renton workers, and a substantial number of furloughs are likely, though perhaps beginning only after the normal holiday break for Christmas and New Year’s, which typically runs from Christmas Eve through New Year’s Day.
Last week, FAA Administrator Steve Dickson pushed out approval for the MAX to fly passengers again into next year, and then told Boeing CEO Dennis Muilenburg in a meeting in Washington, D.C., to dial down public statements suggesting a return to service was imminent.
Privately, officials identified mid-February as the new target for FAA clearance, assuming no further slips in the schedule.
The safety agency has not yet completed its review of the software fix Boeing developed for the new flight control system that activated erroneously on the two MAX crash flights and repeatedly forced the down the nose of each of the jets.
In addition, both the FAA and foreign regulators are assessing how pilots will handle the changes to the flight control systems and what training will be required before a pilot can fly the jet with passengers aboard.
Muilenburg had said in October that a production stoppage or a further cut in the production rate could be necessary if the FAA approval process for a return to service extended into 2020.
More than 800 MAX aircraft are now grounded worldwide. About 500 of those built since the grounding are parked around the Seattle area and at Moses Lake in Eastern Washington, undeliverable for now.
It’s unclear if Boeing will continue production of the 737-based Navy anti-submarine plane, the P-8, which is built on a separate assembly line in Renton and based on a model preceding the MAX. However, that is a low-production line, rolling out just one or two planes a month.
The MAX had been produced at a rate of 52 jets per month until the plane was grounded, and since then was cut back to 42 jets per month.
The impact of a MAX shutdown would ripple out through Boeing’s 737 supply chain and would idle aerospace workers across the nation and internationally.
Among the most affected suppliers is Spirit AeroSystems of Wichita, Kansas, which assembles the MAX fuselages and sends them to Renton by train.
Once production is slowed or stopped, it’s not easy to ramp up again. For that reason, since the grounding in March, Spirit has continued to maintain the pregrounding build rate of 52 fuselages a month even though Boeing was accepting only 42 per month.
That has meant fuselages stacking up in Wichita even as completed jets stacked up in Washington state. A complete halt in Renton will likely force a halt in Wichita.
Another big supplier is CFM International, a joint venture between GE and Safran of France, which builds the jet’s new LEAP engines at facilities around the U.S.
Smaller suppliers could potentially be even more affected.
In the currently booming U.S. job market, a small supplier that has to lay off workers for as long as 60 days is likely to lose those employees as they find work elsewhere. That means hiring and training new people in order to bring production back up.
A shutdown would also amplify the financial impact of the grounding on Boeing.
While production is stopped, many fixed overhead costs continue. Because Boeing’s costs during any shutdown period will be spread over many fewer aircraft than previously projected, it’s likely the company would have to announce another big accounting write-off when it reports its quarterly earnings in January.
Through October, Boeing had already projected $2.7 billion in extra costs due to the previous 20% production cut, in addition to a $5.6 billion write-off to cover compensation to suppliers and customers.
Even though a shutdown was somewhat anticipated, the stock may take a hit on Monday.
There are also broader impacts: Boeing is the country’s largest exporter, and the inability to deliver 737 MAXs to overseas airlines has already widened the 2019 trade deficit. As the U.S. heads into a presidential election year, job losses from a production shutdown will heighten political concern and possibly add to pressure on the FAA to speed up its review of the MAX.
The current discussions around weighing a Renton shutdown were first reported Sunday by the Wall Street Journal.
Boeing had no comment Sunday, and simply repeated a statement sent out Thursday that “we will continue to assess production decisions based on the timing and conditions of return to service.”
Dominic Gates: 206-464-2963 or [email protected]; on Twitter: @dominicgates.
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D-shaped shaft or splined shaft have clearance that has to be taken out somehow. Usually on a D-shaft there is a setscrew set against the flat. Splines are a poor choice for reversing loads. If not pre-loaded, they fret (particularly in high-vibration environments such as aircraft,) producing fod and increasing the clearance and eventually leading to a large amount of backlash.
As to failure of shaft or AOA vane, normally the counterweight will respond to gravity and point straight down. I would guess it is possible for a design to say if pointed straight down- absent other issues-signals , the sensor attached would give either a plus or minus AOA indication. if the sensor is detached an internal or designed-in weight could do the same thing and return a signal saying level flight.
And as to attachment and fretting-- locking tapers on shafts and fasteners have been used for decades- they do not slip, fret, or get pulled out easily - check standard machine tool cutter attachment methods or look up ' Taper-lok ' fasteners used in aircraft industry for over 50 years.
MY point is and was - IMO- the AOA sensor needs a more robust mechanical design instead of the flat plate and spring design methods as used on 1920's biplanes used for airspeed as on the Travelair ..
Last edited by Grebe; 16th Dec 2019 at 04:02. Reason: fat fingers
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The set screws and gears everyone is blaming don't play any part in the operation of the sensor when the A/C is in flight.
They keep the sensor in a faired position on the ground.
They keep the sensor in a faired position on the ground.