The Boeing 737 use of the Roller Coaster method of manual stab trim
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One simple alerting function that was already used to great effect by Douglas was the good ol’ “Bitching Betty” voice screaming “STABILIZER MOTION!!!” every time the trim moved for more than a few seconds, no matter how it was commanded.
In the “Boeing” 717 found that to be absolutely instinctive....
In the “Boeing” 717 found that to be absolutely instinctive....
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Doesnt the "roller Coaster' require a whole lot of altitude and speeds far less than 250 kts? I was under the impression that even with the NG, it was about impossible over 200 kts to even budge the wheel...even with the knee buster out (hence both pilots working the wheels was introduced) hahahha, just picturing trying to get the handle out when it is spinning madly...
Aside from that, what may have worked in the -200, may not work in the MAX...a far slicker ac, and a much different beast.
(like doing donuts in the snow with a vega vs a corvette)
Aside from that, what may have worked in the -200, may not work in the MAX...a far slicker ac, and a much different beast.
(like doing donuts in the snow with a vega vs a corvette)
Last edited by turbidus; 21st Mar 2020 at 19:19.
I think some of the problems may come from primacy. On many light aircraft, including popular training ones, the elevator is the majority of the pitch control surface and the trim a much smaller tab. This is completely reversed on most jet transports and leaves the trim with much more authority than the elevator (for sound aerodynamic reasons), which IMO doesn’t get emphasised enough in training.
Most exercises can be successfully completed by a) keeping the aircraft roughly in trim and manoeuvring on the elevator or b) stopping a runaway by disconnecting the trim. It is rare to be presented with a scenario where trim and elevator are in total opposition, at which point there is usually a consistent winner...
Most exercises can be successfully completed by a) keeping the aircraft roughly in trim and manoeuvring on the elevator or b) stopping a runaway by disconnecting the trim. It is rare to be presented with a scenario where trim and elevator are in total opposition, at which point there is usually a consistent winner...
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Wonder what this MAX is practicing???
EDIT: Interesting the speed, about 150 to 220? 2 -8's and a -9 MAX ac out today, doing all sorts of crazy stuff....
EDIT: Interesting the speed, about 150 to 220? 2 -8's and a -9 MAX ac out today, doing all sorts of crazy stuff....
Last edited by turbidus; 24th Mar 2020 at 19:28.
(Pax). Indeed.
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okay, I want you pilots to keep in mind you are driving the most advanced, safest, aircraft that Boeing offers..
That being said, every once in a while, we are not exactly sure when, you may have to descend from FL37 to, well about, 2500 feet AGL, hitting the speed brakes on the way to get the ac to less than 200 kts...all good so far, right?
Then, you will have to perform a "roller coaster" technique" to save the ac...
(sorry, this is not the vomit comet procedure, but close)
Dont worry, the following technique will be added to the seatback pamphlets so the pax wont be scared sh**less...
Hey, both of you, pay attention, handles out, both hands on that wheel...now...
Should you be successful, and avoid CFIT, feel free to return to FL 37...
Thank you for flying the brand new, 17th century designed, 737MAX!
Oh, and as a reminder, while you are trying to save the ac, dont forget to inform those annoying little ****z at ATC what you are doing....they can get soooo annoying with that 35K drop...
When you get back to report, keep in mind that you have been flying an A321 neo.....
Thank you for flying the new and improved 737MAX!
That being said, every once in a while, we are not exactly sure when, you may have to descend from FL37 to, well about, 2500 feet AGL, hitting the speed brakes on the way to get the ac to less than 200 kts...all good so far, right?
Then, you will have to perform a "roller coaster" technique" to save the ac...
(sorry, this is not the vomit comet procedure, but close)
Dont worry, the following technique will be added to the seatback pamphlets so the pax wont be scared sh**less...
Hey, both of you, pay attention, handles out, both hands on that wheel...now...
Should you be successful, and avoid CFIT, feel free to return to FL 37...
Thank you for flying the brand new, 17th century designed, 737MAX!
Oh, and as a reminder, while you are trying to save the ac, dont forget to inform those annoying little ****z at ATC what you are doing....they can get soooo annoying with that 35K drop...
When you get back to report, keep in mind that you have been flying an A321 neo.....
Thank you for flying the new and improved 737MAX!
okay, I want you pilots to keep in mind you are driving the most advanced, safest, aircraft that Boeing offers..
That being said, every once in a while, we are not exactly sure when, you may have to descend from FL37 to, well about, 2500 feet AGL, hitting the speed brakes on the way to get the ac to less than 200 kts...all good so far, right?
Then, you will have to perform a "roller coaster" technique" to save the ac...
(sorry, this is not the vomit comet procedure, but close)
Dont worry, the following technique will be added to the seatback pamphlets so the pax wont be scared sh**less...
Hey, both of you, pay attention, handles out, both hands on that wheel...now...
Should you be successful, and avoid CFIT, feel free to return to FL 37...
Thank you for flying the brand new, 17th century designed, 737MAX!
Oh, and as a reminder, while you are trying to save the ac, dont forget to inform those annoying little ****z at ATC what you are doing....they can get soooo annoying with that 35K drop...
When you get back to report, keep in mind that you have been flying an A321 neo.....
Thank you for flying the new and improved 737MAX!
That being said, every once in a while, we are not exactly sure when, you may have to descend from FL37 to, well about, 2500 feet AGL, hitting the speed brakes on the way to get the ac to less than 200 kts...all good so far, right?
Then, you will have to perform a "roller coaster" technique" to save the ac...
(sorry, this is not the vomit comet procedure, but close)
Dont worry, the following technique will be added to the seatback pamphlets so the pax wont be scared sh**less...
Hey, both of you, pay attention, handles out, both hands on that wheel...now...
Should you be successful, and avoid CFIT, feel free to return to FL 37...
Thank you for flying the brand new, 17th century designed, 737MAX!
Oh, and as a reminder, while you are trying to save the ac, dont forget to inform those annoying little ****z at ATC what you are doing....they can get soooo annoying with that 35K drop...
When you get back to report, keep in mind that you have been flying an A321 neo.....
Thank you for flying the new and improved 737MAX!
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Centaurus.
Hi C
I was in the sim the other day for my Recurrent training. Then LPC/OPC the next day.
I was a bit distracted by the Corona stuff and was rather eager to get the thing over and evacuate London ASAP.
I had a few things I wanted to try with regards the -800 and Max handling, but we ran out of time.
We DID cover runaway trim. Then we did as a separate exercise a outoff trim sequence , were we started with FO PF with both elec trim switches in Cut out , 280kts and stab ND trimmed so FO could just hold it at level flt:
I was shocked to find that it was so hard to get half a turn at a time, and as I predicted only as we slowed down towards 230 kts for this specific condition was it possible to get the 40 plus turns we needed to get in trim.
At one point we both gave trim inputs and the Sim Control Loading promptly dropped out.
So!
Providing the Flight Test Data and the therefrom derived Control Loading Data is correct , I can only conclude the Max will never fly again!
Lets just be glad the 737-800 is not affected,,,,,,,
Regards
Cpt B
I was in the sim the other day for my Recurrent training. Then LPC/OPC the next day.
I was a bit distracted by the Corona stuff and was rather eager to get the thing over and evacuate London ASAP.
I had a few things I wanted to try with regards the -800 and Max handling, but we ran out of time.
We DID cover runaway trim. Then we did as a separate exercise a outoff trim sequence , were we started with FO PF with both elec trim switches in Cut out , 280kts and stab ND trimmed so FO could just hold it at level flt:
I was shocked to find that it was so hard to get half a turn at a time, and as I predicted only as we slowed down towards 230 kts for this specific condition was it possible to get the 40 plus turns we needed to get in trim.
At one point we both gave trim inputs and the Sim Control Loading promptly dropped out.
So!
Providing the Flight Test Data and the therefrom derived Control Loading Data is correct , I can only conclude the Max will never fly again!
Lets just be glad the 737-800 is not affected,,,,,,,
Regards
Cpt B
This may have come up in a previous thread, but has it been conclusively shown that in a severe out-of-trim/high IAS condition - albeit a less likely scenario in an NG - trim wheel forces are significantly different in the -800 compared to the Max ?
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Identical system!
Dear David
How are You doing in these Corona times?
A bit of sarcasm on my previous post.
The system is identical minus the MCAS computer and associated electric wiring AND the new Cutout switches.As fare as I recall.
So, I would not be surprised if the old roller-coaster maneuver will be mandatory in future 737-800 training.
What the 737-800 has going for it is the statistics!
To me it was interesting to see the ABSOLUTE need to reduce speed to gain control, unfortunately I did not have a chance to fly the full envelope and I do forget the CofG and were we started on the trim scale.
When I did my 737 SFI in 2003 the Rudder Hardover was still fresh and we did the relevant recovery and I remember thinking " WTF, This better not happen at low level!"
Fortunately they fixed the problem.
The MCAS in total isolation might not be enough to permanently ground the MAX , BUT, paired with the useless manual trim wheel AND the never-ending row of old sins popping up leads me to think the MAX need a aerodynamic replacement form any MCAS , or its end of the road!
Strangely silent it has been!
Remember.
Boeing has at least 2 if not 3 year until ANY of the new MAXs is need now.
Why would Canada, EASA China or FAA for that matter use one more calorie on this until Boeing can prove it perfect without the added MCAS risk!
For that risk is unacceptable, trust me, the poor Ethiopians were doomed once past ca 260kts and no thrust reduction considered.
A horrible horrible way to go,,,
Lastely
Never understood why Boeing never , in parallel, developed some strakes or whatever it is called, F16 style or like the Beech1900D!
Regards
Cpt B
How are You doing in these Corona times?
A bit of sarcasm on my previous post.
The system is identical minus the MCAS computer and associated electric wiring AND the new Cutout switches.As fare as I recall.
So, I would not be surprised if the old roller-coaster maneuver will be mandatory in future 737-800 training.
What the 737-800 has going for it is the statistics!
To me it was interesting to see the ABSOLUTE need to reduce speed to gain control, unfortunately I did not have a chance to fly the full envelope and I do forget the CofG and were we started on the trim scale.
When I did my 737 SFI in 2003 the Rudder Hardover was still fresh and we did the relevant recovery and I remember thinking " WTF, This better not happen at low level!"
Fortunately they fixed the problem.
The MCAS in total isolation might not be enough to permanently ground the MAX , BUT, paired with the useless manual trim wheel AND the never-ending row of old sins popping up leads me to think the MAX need a aerodynamic replacement form any MCAS , or its end of the road!
Strangely silent it has been!
Remember.
Boeing has at least 2 if not 3 year until ANY of the new MAXs is need now.
Why would Canada, EASA China or FAA for that matter use one more calorie on this until Boeing can prove it perfect without the added MCAS risk!
For that risk is unacceptable, trust me, the poor Ethiopians were doomed once past ca 260kts and no thrust reduction considered.
A horrible horrible way to go,,,
Lastely
Never understood why Boeing never , in parallel, developed some strakes or whatever it is called, F16 style or like the Beech1900D!
Regards
Cpt B
