aerotech777
Topic Author
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Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 3:53 am

Hi,

It seems it’s difficult to handle (to reduce the speed and altitude) jet aircraft during approach and landing.

a) I am wondering if this occurs in all jet aircraft or only in certain jet aircraft.

b) What are the causes of this problem besides approach idle (high idle)?

c) Which of two may cause more go-around: difficult handling of aircraft during approach/landing or complying with ATC requests? (If there is conflict between the two)

d) How often pilots perform a go-around?

Feedback appreciated

Regards
 
sccutler
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 5:03 am

Jet aircraft handle quite well; presuming a well-planned and executed stabilized approach, the planes are very docile.

Nearly all go-arounds are the result of inadequate separation - aircraft ahead not clearing the runway in time to assure safe landing zone for the next landing aircraft.
...three miles from BRONS, clear for the ILS one five approach...
 
jetboy757
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 5:09 am

I'm an air traffic controller and the majority of the go-arounds that I've seen are due to aircraft being to high, to fast, not configured, or passenger problems such as not being seated or someone in the bathroom. There are the occasional preceding aircraft doesn't clear the runway in time, but more so the other reasons. For the 2 years that I've been a controller I've seen maybe 3 go-arounds because the runway wasn't clear. I've seen maybe 2 go-arounds a week because of the aircraft not being configured, etc...

[Edited 2010-05-23 22:17:40]
 
cobra27
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 5:41 am

Does computer control help at low speed (digital fly by wire) help at low speed?
For example 737 doesn't have fbw, but surely it ha sother computer than make handling easier at low speed?
 
pilotpip
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 6:31 am

No computer needed. Flaps and Slats provide more lift (and drag) for lower speeds. Most jets like the 737 will have spoilers to help with roll rates. While jets (and any other aircraft) will get more sluggish at low speeds they will remain completely controllable as long as you stay at a safe speed. Flight idle on the engines isn't really a big deal because once your configuration is set and you're on a stabilized approach the thrust levels are far above idle.

In four years, I've done four go arounds in the aircraft. Two in one day going into ORD in strong winds. One was due to a heavy not clearing fast enough in SAV. Things get a little busy but it's nothing insane. We train for it in the sim and there are standard callouts and procedures to follow to make sure things go right. It's nowhere near an emergency event. In fact, it's in our normal procedures. A full stop landing isn't an assured thing until the reversers are deployed. In every case a go around was the safe alternative to landing. If something isn't right, get up to a safe altitude and either start over, or see what the problem is and figure out what you can do about it. There have been far too many crashes because the crew tried to force it in when they should not have.

And for the O/P, I'm probably going to ruffle the ATC guys' feathers a bit but the PIC has ultimate authority. There's this simple little word we have when we don't like ATC's instructions. "Unable". It doesn't have to be used very often but when we have to use it the guy sitting at the scope sounds a little mad.

[Edited 2010-05-23 23:36:03]
DMI
 
tdscanuck
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 6:41 am

Quoting cobra27 (Reply 3):
Does computer control help at low speed (digital fly by wire) help at low speed?

It can. It depends on what the control laws are (a FBW in direct mode could be worse than a non-FBW operating normally). But, in general, a FBW with typical control laws will be more predictable at low speed than an equivalent non-FBW aircraft.

Quoting cobra27 (Reply 3):
For example 737 doesn't have fbw, but surely it ha sother computer than make handling easier at low speed?

It depends on how you define computer. There are elements in the control system that help improve handling characteristics at low speed, but not a computer in the fly-by-wire sense.

Tom.
 
cobra27
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 24, 2010 8:46 pm

Quoting tdscanuck (Reply 5):
It depends on how you define computer. There are elements in the control system that help improve handling characteristics at low speed, but not a computer in the fly-by-wire sense.

Yes, 737 has Control wheel steering cws, (this must be computer controlled) and no fly by wire. For example concorde had analog fly by wire, it was basically the same the same as cable only withhout them. Digital fly by wire such as A320 and 777 have different outputs depending on speed
 
tdscanuck
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RE: Jet Aircraft Handling During Approach & Landing

Tue May 25, 2010 5:31 am

Quoting cobra27 (Reply 6):
Yes, 737 has Control wheel steering cws, (this must be computer controlled)

It is, but not by the flight control computers. CWS is usually implemented in the autopilot.

Quoting cobra27 (Reply 6):
Digital fly by wire such as A320 and 777 have different outputs depending on speed

There's no reason that an analog system (either analog FBW a la Concorde, or "hardwire" analog like a 737) can't vary outputs on speed. It's just messier. There's a reason that so many cable systems on non-FBW control systems have so many levers, cams, pulleys, and linkages...they're implementing analog control laws.

Tom.
 
pilotpip
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RE: Jet Aircraft Handling During Approach & Landing

Wed May 26, 2010 1:05 am


View Large View Medium
Click here for bigger photo!

Photo © Ricardo Morales - flyAPM



See that tube about midway up the verticle stabilizer? That's a great example of a mecahnical means to limit a control. That pitot tube is attached to a linkage that limits rudder travel as the aircraft accellerates. It's worked well for 40 years now.
DMI
 
DashTrash
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RE: Jet Aircraft Handling During Approach & Landing

Wed May 26, 2010 3:22 am

Quoting aerotech777 (Thread starter):
It seems it’s difficult to handle (to reduce the speed and altitude) jet aircraft during approach and landing.

It's all about planning. Spoilers are there for mistakes in said planning. As you get more experience in the airplane, you learn at what point you need to reduce thrust to slow enough to configure the airplane.

Quoting aerotech777 (Thread starter):
c) Which of two may cause more go-around: difficult handling of aircraft during approach/landing or complying with ATC requests? (If there is conflict between the two)

All of the go arounds I've done were because another airplane didn't clear the runway, or there was a conflict between us and another airplane at a runway intersection (PHL).

Quoting aerotech777 (Thread starter):
d) How often pilots perform a go-around?

Once every few months. They're not all that common, but at some point you will do one.
 
pilotpip
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RE: Jet Aircraft Handling During Approach & Landing

Wed May 26, 2010 3:30 am

Quoting DashTrash (Reply 9):
Spoilers are there for mistakes in said planning.

I don't agree with that. Some newer aircraft, the 175 is a great examples will not go down and slow down. I use the speedbrakes MUCH more in the 175 than I do 170. You need them even in normal situations.
DMI
 
DashTrash
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RE: Jet Aircraft Handling During Approach & Landing

Thu May 27, 2010 2:54 am

Quoting pilotpip (Reply 10):
I don't agree with that. Some newer aircraft, the 175 is a great examples will not go down and slow down. I use the speedbrakes MUCH more in the 175 than I do 170. You need them even in normal situations.

I think most modern aircraft are like that. With the X, I could do around 3000 fpm+ downhill without the boards if I didn't have to worry about the speed. Thumb it up to 500 - 1000 fpm around 13 - 14000 ft and begin slowing to 250, then around 15-1700 fpm at 250 clean. Anything over 1700 and you had to add drag. It was all about planning.

Never flew your 175, so it could be different, either that, or I'm just a better pilot than you.  (I kid....)
 
mandala499
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RE: Jet Aircraft Handling During Approach & Landing

Thu May 27, 2010 10:52 am

Quoting cobra27 (Reply 3):
Does computer control help at low speed (digital fly by wire) help at low speed?
For example 737 doesn't have fbw, but surely it ha sother computer than make handling easier at low speed?

The FBW can be programmed to provide a roll rate output, hence it can make the outcome identical throughout the operating speed range, and in various configs. Hence...

Quoting tdscanuck (Reply 5):
But, in general, a FBW with typical control laws will be more predictable at low speed than an equivalent non-FBW aircraft.

Now,

Quoting tdscanuck (Reply 5):
There are elements in the control system that help improve handling characteristics at low speed, but not a computer in the fly-by-wire sense.

The 737 has computers on it's flight control system, it's just that it's not an digital/electronic one... such as mechanical ratio-changing stuff... Open up the flight control pages on the 737 manual and you have boxes and words such as "elevator feel computer"...   

I guess in this day in age, when one sees the word "computer", everyone expects that "computer" to be a digital electronic one... aviation, have long used various gizmos and contraptions.
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
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Starlionblue
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RE: Jet Aircraft Handling During Approach & Landing

Thu May 27, 2010 11:37 am

Quoting mandala499 (Reply 12):

I guess in this day in age, when one sees the word "computer", everyone expects that "computer" to be a digital electronic one... aviation, have long used various gizmos and contraptions.

The original meaning of "computer" is in fact "person who performs calculations/computations". This definition is hundreds of years old. So in essence, a pilot carrying out calculations is a a "computer". Nowadays a lot of the work that used to be carried out by the fleshbag computer has been taken over by the electronic computers.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
aerotech777
Topic Author
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RE: Jet Aircraft Handling During Approach & Landing

Thu May 27, 2010 5:40 pm

Hi,

Here is a quote from Flight Safety Foundation:

"The flight Safety Foundation Approache and Landing Accident Reduction (ALAR)Task Force found that unstabilized approaches (i.e., approaches conducted either low/slow or high/fast) were a causal factor in 66% of 76 approach and landing accidents and serious incidents worldwide in 1984 through 1997

The task force said that although some low-energy approaches (i.e., low/slow) resulted in loss of aircraft control, most involved CFIT because of inadequate vertical-position awareness.

The task force said that the high-energy approaches (i.e., high/fast) resulted in loss of aircraft control, runway overruns and runway excursions, and contributed to inadequate situational awareness in some CFIT accidents.

The task force also found that flight-handling difficulties (i.e., the crew’s inability to control the aircraft to the desired flight parameters [e.g., airspeed, altitude, rate of descent]) were a causal factor in 45% of 76 approach and landing accidents and serious incidents.

The Task Force said that flight-handling difficulties occured in situations that includes rushing approaches, attempts to comply with demanding ATC clearance, adverse wind condition and improper use of automation."

Regards
 
pilotpip
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RE: Jet Aircraft Handling During Approach & Landing

Sat May 29, 2010 3:54 am

Quoting DashTrash (Reply 11):
Never flew your 175, so it could be different, either that, or I'm just a better pilot than you. (I kid....)

You probably are. Passengers give me lots of dirty looks after my landings  
DMI
 
DashTrash
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RE: Jet Aircraft Handling During Approach & Landing

Sat May 29, 2010 9:40 pm

Quoting pilotpip (Reply 15):
You probably are. Passengers give me lots of dirty looks after my landings

At least they survive your landings. It's anyone's guess when its my leg. 
 
Longhornmaniac
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RE: Jet Aircraft Handling During Approach & Landing

Sat May 29, 2010 10:09 pm

Quoting pilotpip (Reply 15):

You probably are. Passengers give me lots of dirty looks after my landings

  

Quoting DashTrash (Reply 16):
At least they survive your landings. It's anyone's guess when its my leg.

  

Good stuff, guys!

Cheers,
Cameron
Cheers,
Cameron
 
andyinpit
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 31, 2010 5:27 pm

Quoting pilotpip (Reply 4):
And for the O/P, I'm probably going to ruffle the ATC guys' feathers a bit but the PIC has ultimate authority. There's this simple little word we have when we don't like ATC's instructions. "Unable". It doesn't have to be used very often but when we have to use it the guy sitting at the scope sounds a little mad.

You better have a very, very good reason for ignoring an ATC instruction...because you deciding not to follow yours, could very easily put you in conflict with someone else.
 
413X3
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RE: Jet Aircraft Handling During Approach & Landing

Mon May 31, 2010 8:10 pm

Quoting andyinpit (Reply 18):
You better have a very, very good reason for ignoring an ATC instruction...because you deciding not to follow yours, could very easily put you in conflict with someone else.

what, do you think they say unable just for fun?
 
jetboy757
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RE: Jet Aircraft Handling During Approach & Landing

Wed Jun 02, 2010 9:31 am

There's a difference between saying "unable" and not complying with an ATC instruction.
 
pilotpip
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RE: Jet Aircraft Handling During Approach & Landing

Mon Jun 07, 2010 1:36 am

Quoting andyinpit (Reply 18):

You better have a very, very good reason for ignoring an ATC instruction...because you deciding not to follow yours, could very easily put you in conflict with someone else.

I'm very well of that.

"§ 91.3 Responsibility and authority of the pilot in command.
(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.

(b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

(c) Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator."

Nowhere in there does it say, "The pilot must have a good reason to say they're unable to comply". Nowhere in there does it say ATC is responsible. It's says PIC.

Telling ATC that you're unable to comply is in no way ignoring an instruction. On the other hand it demonstrates that you're aware enough of the conditions, and the capabilities of yourself, ATC and the aircraft to say you can't comply. Great example would be our departure this morning from CMH. We were cleared for takeoff on runway heading. We were painting a nasty cell about 10 miles away. We said unable and requested a left turn to a heading of 230 to avoid the cell.
DMI
 
tdscanuck
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RE: Jet Aircraft Handling During Approach & Landing

Mon Jun 07, 2010 4:44 am

Quoting pilotpip (Reply 21):
Nowhere in there does it say, "The pilot must have a good reason to say they're unable to comply".

That's basically what this part means (my emphasis added)

Quoting pilotpip (Reply 21):
the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

You're only allowed to deviate from the rules (including the rule that you obey ATC) to the extent required to meet the emergency...that means you actually need to have an emergency, and you can only deviate as much as necessary to mitigate the emergency. That's the "good reason."

Tom.
 
alwaysontherun
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RE: Jet Aircraft Handling During Approach & Landing

Mon Jun 07, 2010 11:25 am

Hi all,

the other day we did an interesting approach into Vitória (Brazil), where we followed the runway at appr. 1500´ while descending and then we came with a hard right turn all the way around (360º) and landed……smooth as a baby´s bottom.
Very nice, such an "aggressive" turn……….

Anyway, my question is; why was it when we went through this hard right turn, I didn´t see the aileron(s) move?
The spoilers (air brakes?) moved a bit for a few seconds sometimes.

Are the ailerons restricted when flying at low speed?
How did we make the turn if it was not for the ailerons?

It was on a 737-700, FYI.

Cheers,

###I´m always on the Run###
"Failure is not an option, it comes standard in any Windows product" - an anonymous MAC owner.
 
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Starlionblue
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RE: Jet Aircraft Handling During Approach & Landing

Mon Jun 07, 2010 12:17 pm

- The spoilers act as additional roll control at low speeds, complementing the ailerons.
- The ailerons often don't need to move so much.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: Jet Aircraft Handling During Approach & Landing

Tue Jun 08, 2010 2:32 am

Quoting alwaysontherun (Reply 23):
Anyway, my question is; why was it when we went through this hard right turn, I didn´t see the aileron(s) move?
The spoilers (air brakes?) moved a bit for a few seconds sometimes.

Most commercial jets are very close to neutral spiral stability...they tend to hold whatever bank they're at unless you command some roll rate. As a result, the only time you need to deflect ailerons is when you're rolling in or rolling out of the turn...during the turn itself, the ailerons should be nearly faired.

In a perfectly spiral stable aircraft, you wouldn't see any deflection at all while you were in the turn (assuming a constant bank turn).

Tom.

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