william
Posts: 1570
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In Rough Weather Who's Flying?...Autopilot?

Wed Mar 19, 2003 2:33 pm

I was on an United flight some time ago that descended through some rough weather(thunderstorm,lots of lightning). The aircraft was the old reliable 737-200. Outboard spoilers were engaged at the beginning of the descent and it was a ROUGH ride down to the outer maker (did I say ROUGH?) The aircraft never rolled that much,but there was much vertical dropping. My question is in that type of sitauation,was it most likely the aircraft was on autopilot on the way down?

The reason I state this is because of how level the wings were even keel though we were hitting hard turbulence descending. The ailerons did not move much,and neither did the spoilers. Usually you can feel the pilot over correcting a tad bit,on autopilot you feel less of it. What do you think? What is SOP when decending in turbulence generated by a nearby storm?

I am just a frequent flyer(loving it,not complaining) who logged many a miles upstairs,and notice little quirks like this.
 
av8rphx
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 19, 2003 3:53 pm

It really depends on the PF (Pilot flying). I know some pilots prefer to ride out turbulence with manual control. But some pilots including myself prefer to use autopilot in these situations,just for the mere fact that manual control can lead to over-correction in certain instances.
 
CX Flyboy
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 19, 2003 6:14 pm

Unless I am already established on the ILS, I will tend to leave the autopilot in, and monitor it. The role of the pilot these days is so much more than simply flying the plane. In conditions like that, the autopilot does a good job of maintaining aircraft stability and speed control. Flying manually in tough conditions takes you completely out of the loop as you are concentrating only on flying, especially in the worst of conditions. In a two-man aircraft, this is not desireable.

On the ILS however, the autopilot and autothrottle can sometimes be a little slow to react and although Boeing says that it will do a good job, I, and many other prefer to fly manually. This lessens the sharp FBW reactions to each and every turbulent movement and allows a much smoother approach. It can also lessen the onset of a GPWS windshear warning, requiring a mandatory go-around. However, manual go-arouns tend to be more sloppy than ones done with the autopilot in, merely because we don't do many of them, and because of that, in conditions where a go-around is a real possiblity, it is wise to consider leaving the autopilot in until a landing is assured.
 
william
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RE: In Rough Weather Who's Flying?...Autopilot?

Fri Mar 21, 2003 3:50 am

So when I saw the outboard spoilers engaged at the beginning of our descent,was that an autopilot input or something the pilot would engage to assist the autopilot?

Just asking for a "guestimate".
 
CX Flyboy
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RE: In Rough Weather Who's Flying?...Autopilot?

Fri Mar 21, 2003 9:40 am

No autopilot is capable of extending the speedbrakes as far as I know. The pilot will do this to assist the autopilot. If it gets to the stage where the autopilot can no longer fly the preprogrammed path without overspeeding the aircraft, on the 777 and 744, DRAG REQUIRED comes up in the FMC window to let the pilot know that speedbrakes are needed to slow the aircraft down a bit in order to help the descent.
 
lmml 14/32
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RE: In Rough Weather Who's Flying?...Autopilot?

Mon Mar 24, 2003 2:46 am

Speed brakes from TOD right down to the outer marker? Strange. A B732 can bleed off speed very quickly. The speedbrakes themselves cause a very noisy vibration. With the speed brakes extended the plane tends to exagerate the roll input.
 
william
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RE: In Rough Weather Who's Flying?...Autopilot?

Tue Mar 25, 2003 10:54 am

The speedbrakes were up until we leveled off at what I guess was the outer marker. Upon leveling off,the slats and flaps were lowered. This was at the old Austin Mueller airport in Texas and it was 1 am. No traffic of any kind.

Thats interesting, the the autopilot is not capable of extending speedbrakes or spoilers for speed control. If an aircraft was on autoland CAT 3(landing approach) ,the autopilot would use the spoilers for roll control would it not? (Always a sight to see).
 
GE
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RE: In Rough Weather Who's Flying?...Autopilot?

Tue Mar 25, 2003 7:38 pm

William:
Yes the autopilot may extend the spoilers for roll control if necessary, these spoilers work in conjunction with the ailerons.
What Cx Flyboy meant was that the spoilers cannot be extended by the autopilot for the purpose of reducing speed/ increasing rate of descent. They can, however, be used together with the ailerons for roll control.
You may also want to know that on some planes, the spoilers used for roll control are not necessarily all the spoilers on the plane. Not all the spoilers are needed for roll anyway, so they aren't designed to be deployed when used with ailerons for roll, or they may simply extend partially. Of course on the ground all spoilers are deployed to max. deflection.

Regards,
Russell J.
 
Rick767
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RE: In Rough Weather Who's Flying?...Autopilot?

Tue Mar 25, 2003 8:20 pm

Like GE said, on the 757 only some of the spoiler panels are used for both roll control and speedbrake in the air. On the ground, all panels raise with speedbrakes deployed.

The 767 is an exception, all the spoiler panels are used for roll control and speedbrake, both in the air and on the ground (if memory serves...).

"So when I saw the outboard spoilers engaged at the beginning of our descent,was that an autopilot input or something the pilot would engage to assist the autopilot?"

That would be a pilot input to increase the rate of descent to get the aircraft back on the idle descent path. Once back on the appropriate descent path the speedbrakes can be re-stowed for a normal descent. This is common practice when we are given a slightly late descent from ATC (so the aircraft passes the FMC-computed T/D point before a descent clearance is issued).

It can also be required with descent in tailwind conditions where the high ground speed will result in the angle of descent less than the idle descent path. Like Cx_flyboy said, the "DRAG REQUIRED" FMC message is the one to watch for here.
I used to love the smell of Jet-A in the morning...
 
william
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RE: In Rough Weather Who's Flying?...Autopilot?

Tue Mar 25, 2003 10:52 pm

Thank you for that info,it was on 757 flights that I noticed the outboard and inboard spoilers were used for roll control in landing configuration.

GE,it is true that on some Airbuses (A310) the outboard spoilers are for roll control,since they do not have ailerons..

Thank you again for your responses.
 
bio15
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 5:07 am

A310 has no ailerons??? Can anyone confirm that please?

-Alfredo
 
A330
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 8:10 am

A310 combines in roll aileron and some of the speed brakes, just like any other Airbus.

Speed-brake deployment is ALWAYS pilot controlled by my knowledge.
Spoilers can be deployed automatically if on RTO (Boeing) and ARMED.
Shiek!
 
Rick767
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 8:51 am

"Spoilers can be deployed automatically if on RTO (Boeing) and ARMED."

I assume this is also the case for the Airbus though? We get full auto speedbrake in an RTO by bringing the thust lever to idle (assuming they are ARMED). We would also get full speedbrake deployment (without the need to have the speedbrakes armed) by moving either reverse thrust lever to the interlock stop (so even if we do not ARM the speedbrakes for landing / RTO, as soon as we apply reverse thrust on the ground, all speedbrakes will deploy automatically).

Would be interested to hear if this is also the case for the bus.
I used to love the smell of Jet-A in the morning...
 
william
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 12:53 pm

After consulting my trusty "Modern Commercial Aircraft",book,and looking at the A310 schematics. NO,the A310 has NO outboard airlerons,they are fixed. Roll control is achieved through the spoilers.

Check again A330.
 
GE
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 6:50 pm

For the A320 the 4 outboard spoilers are used for roll control in conjuction with the aileron (only has outer aileron).

Regards,
Russell J.

[Edited 2003-03-26 11:09:05]
 
A330
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 7:04 pm

Rick,

On Airbus, we do not have the RTO option, only Autobrake MAX which is the same actually. Spoilers must be armed whenever the Landing gear is down. (Loop with gear up/down)

In the case of the B737.200 that kept its speed brakes extended during the whole descend, probably, somebody forgot to stow them again!!!! ( we all did it, don't be ashamed!!!) (good airmanship says to keep hand on the speed-brakes whenever deployed)

William, I have never flown the A310 (Sabena had them before my time...) so I stand corrected, thank you.
Shiek!
 
william
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A330

Wed Mar 26, 2003 10:43 pm

A330 in rough weather,as a pilot,do you want the spoilers deployed? Considering the turbulence? My reasoning is that you want the aircraft to, "drop" like a rock through the turbulence. Correct me if I am wrong.

Thank you.

This has been a very enlightening thead. All the systems that work in unison to keep an aircraft on it intended course are indeed fascinating,and something many people, and frequentflyers(myself),take for granted.
 
CX Flyboy
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Mar 26, 2003 11:43 pm

When we descend we do so at the cruising Mach number, until that equals 300kts, then we descend at 300kts to the relevant speed limit (Normally 250kts below 10,000ft). The 777 in VNAV is not very good at keeping speeds, so we allow it to accelerate a little. The speed may be hovering up at as much as 317 or 318kts. Our VMO is 330kts, so there is a small margin in smooth air. If you hit turbulence, descending at these high speeds, you may risk going into the overspeed range and therefore an initial reaction, depending on how bad the turbulence is, and what mode you are flying in, is to pull the speed brakes. This will have the immediate effect of reducing speed away from the overspeed range. Stalling is not really an issue at these speeds and in this regime of flight, overspeed is. After the speed is under control with the speed brake, we can then reduce the speed to give us a more comfortable margin.
 
FDXmech
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RE: In Rough Weather Who's Flying?...Autopilot?

Thu Mar 27, 2003 12:15 am

>>>NO,the A310 has NO outboard airlerons,they are fixed. Roll control is achieved through the spoilers.<<<

The A310 has no outer ailerons but inner ailerons which are utilized full time, coincidentally called ASA's (All Speed Ailerons). A300-600 is the same. Sidenote:The older A300B2/B4's have outboard and inboard ailerons.

Aileron can be seen between outboard and inboard flaps.

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paulc
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RE: In Rough Weather Who's Flying?...Autopilot?

Wed Apr 02, 2003 12:47 am

Slightly off topic - i was at a lecture given by John Farley - a well known UK test pilot who is currently involved with the Lockheed Martin JSF project.

His career as a test pilot led him to fly many different types of aircraft (mainly single seat Harriers in particular) but he did have the occassional go in a comet which was being used for autopilot/autoland trials. He was doing a flight in the comet during one of these tests - he watched in amazment as the aircraft held a steady approach with (I think he said) a 40kt xwind. He also realised that if the autopilot failed and he needed to land he would have to divert to an airfield with a better into wind runway. He also is a strong advocate for automatics in the control of aircraft - the JSF lecture he gave showed this very well.
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