# 737 grounded???

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#### lr27

##### Well-Known Member
That would be about ten times the average rate.

BJC
Depends if you're talking about the USA or the world, I expect. I think in the USA the number is on the order of 80 or 85. In the world, the number is apparently several thousand a day. There are many places where driving is more dangerous than it is here in the USA.

#### lr27

##### Well-Known Member
I wonder how much altitude that "roller coaster" trick to unload the jack screw uses up?

#### BJC

##### Well-Known Member
HBA Supporter
Depends if you're talking about the USA or the world, I expect. I think in the USA the number is on the order of 80 or 85. In the world, the number is apparently several thousand a day. There are many places where driving is more dangerous than it is here in the USA.
The world-wide rate is well over 3,000 per day.

BJC

#### TFF

##### Well-Known Member
Tennessee looses about three people a day to traffic accidents on a down year, all causes. A couple of years ago it was about four. Way too high either way. Fifty states at the same rate is a lot of people you never even hear about. Some states wish it was that low.

#### BJC

##### Well-Known Member
HBA Supporter
Tennessee looses about three people a day to traffic accidents on a down year, all causes. A couple of years ago it was about four. Way too high either way. Fifty states at the same rate is a lot of people you never even hear about. Some states wish it was that low.
If you improve the rate too much, it will hurt Social Security benefits …..

BJC

#### TFF

By the time I get mine, the check will be $3.51. #### BJC ##### Well-Known Member HBA Supporter By the time I get mine, the check will be$3.51.
I would be WAY ahead if I had been allowed to invest my SS payments rather than let the government use them to cover checks written the week before they took the money from me.

BJC

#### davidb

##### Well-Known Member
I wonder how much altitude that "roller coaster" trick to unload the jack screw uses up?
Properly done, you would never descend below the starting altitude. You pull up into a climb before unloading. You pull back again before the pitch goes below level flight. Without specific training or at least some previous knowledge, it’s unrealistic to expect a crew to arrive at that solution. Seems the fact that the stick shaker was activated would contribute to a reluctance to pull up into a climb.

#### Toobuilder

##### Well-Known Member
Log Member
I can sure see how the roller coaster method would be a completely counterintuitive thing for the untrained/unaware. What a HMI nightmare!

##### Well-Known Member
I think the roller coaster method is not applicable once the nose is below the horizon and can't be pulled up. Each time you release the back pressure the nose will drop further, the speed will increase, and the load on the stab will increase. Basically....you lose.

#### Vigilant1

##### Well-Known Member
I think the roller coaster method is not applicable once the nose is below the horizon and can't be pulled up. Each time you release the back pressure the nose will drop further, the speed will increase, and the load on the stab will increase. Basically....you lose.
It would be scarier with the nose down, but to me it still seems likely to still work. The forces on the jackscrew decrease as soon as the elevator is deflected down (yoke forward). Simultaneously run the the electric trim (or turn the manual wheel). The airspeed buildup won't be instant.
The passengers won't be happy, and the food carts will be a mess. But, in the grand scheme of things . . . .

#### Hot Wings

##### Well-Known Member
HBA Supporter
Log Member
It would be scarier with the nose down,
Roll inverted first!?
Where are our dancing bananas when you need them?

#### davidb

##### Well-Known Member
The jack screw loading issue is more of an awareness issue. By that I mean pilots trained on the 737 should understand the dire seriousness of not allowing the stab to get out of trim in the first place. The runaway stab trim procedure is now an immediate action memory procedure. The intent is to stop the runaway before you lose adequate elevator authority. It seems both of these crews were able to do that and did do that— until their further actions/inactions allowed the trim to runaway some more.

#### markaeric

##### Well-Known Member
It sure would have been nice if, you know, an auto-trimming system didn't take precedence over a pilot's inputted trim command. Boeing dropped the ball in so many ways with their design choices on this plane.

#### davidb

##### Well-Known Member
It sure would have been nice if, you know, an auto-trimming system didn't take precedence over a pilot's inputted trim command. Boeing dropped the ball in so many ways with their design choices on this plane.
Again, no auto-trimming system takes precedence over a pilot’s inputted trim command. The MCAS trimming is stoppable and reversible with the normal trim switches.

#### BJC

##### Well-Known Member
HBA Supporter
davidb:

Thanks for your continuing efforts to share facts rather than speculation and pronouncement of guilt wrt the MCAS.

BJC

#### bmcj

##### Well-Known Member
HBA Supporter
Roll inverted first!?
If you recall, Alaskan Airlines flight 261 (an MD-80) did that after. Jack screw failure. The pilots allowed it to roll inverted and advised ATC that they we attempting to fly it inverted. Unfortunately, they didn’t have enough control authority and altitude, and they impacted the bay off the coast of Los Angeles.

#### Hot Wings

##### Well-Known Member
HBA Supporter
Log Member
If you recall, .
I did not remember this when I posted. I do now. That was a complete failure of the jack screw. Not much that crew could do but go along for the ride.........

#### markaeric

##### Well-Known Member
Again, no auto-trimming system takes precedence over a pilot’s inputted trim command. The MCAS trimming is stoppable and reversible with the normal trim switches.
Thank you for the correction. I should have done more due diligence before spouting off misinformation. I had been under the impression that using the trim switches on the control columns only temporarily disabled MCAS for several seconds but didn't provide control of the stab. The following is something that I haven't heard of until now and is from Boeing's Ops Manual Bulletin TBC-19 pulled from http://www.b737.org.uk/mcas.htm :

"In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released."

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