Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Thrust on during flare...Q for AIRBUS test pilots...

Wikiposts
Search
Tech Log The very best in practical technical discussion on the web

Thrust on during flare...Q for AIRBUS test pilots...

Thread Tools
 
Search this Thread
 
Old 25th Mar 2014, 17:29
  #61 (permalink)  
 
Join Date: Jan 2008
Location: ...
Posts: 3,753
Likes: 0
Received 0 Likes on 0 Posts
Actually, I don't think it is a stupid discussion. You and I can fly satisfactorily using our own techniques (dunno about Noodles) but throw a newby in the seat and tell them to use thrust to control the slope and the stick to control the speed and they'd be in all sorts of bother. I certainly don't tell my FOs to do that. If they try, I growl at them. I've seen to many near-splats with the nose still down and the thrust up all because we fell into a bit of a hole. Pull the friggin' stick back a bit, Bloggs!
Offcourse not, cause pitch for path and thrust for speed is much easier to explain. And for a newby much easier to execute. I'm certainly not advocating to change the way we teach flying.

If you would make us two fly the exact same approach in the exact same conditions I doubt you would see any difference in the way it is flown.

From my observations newbee pilots often use a lot more and bigger input on the controls (stick/yoke and thrust levers), more experienced pilots who are used to manual flight make smaller and less input. I believe this is because of better anticipation who the inputs affect each other.

The simple fact though is that pitch and thrust directly affect each other (and not only through underslung engines). SO it really doesn't matter if you say pitch controls speed/path and thrust controls path/speed.
Both statements are true! And as such you are ALL wrong.

Offcourse this is all valid if your approach speed is fixed... This thinking exercise can be even more fun if you allow speed variations. Offcourse this would not be very practical with regard to landing distance calculations.

BTW if you make students do fake approaches and get them to fly level and add power as required you will miraculously find the flare pitch attitude. we are not bleeding off speed at all, we are reducing the rate of descent to zero and if you can fly level while the wheels touch the ground its called a greaser. And because we don't add power we lose speed which helps with reducing the landing distance.

Last edited by 737Jock; 25th Mar 2014 at 17:47.
737Jock is offline  
Old 25th Mar 2014, 17:45
  #62 (permalink)  
 
Join Date: Nov 2011
Location: Home
Posts: 40
Likes: 0
Received 0 Likes on 0 Posts
I am not sure why you are pointing fingers at Noodle.

There is no doubt that flying a jet -manually- one should use his pitch to control airspeed WHILE controlling the thrust to maintain the path he aims for.

They are interconnected as performance factors, so they go hand in hand as said already BUT, you do not control speed with thrust, and you also do not control path by pulling or pushing the yoke. Not in a Boeing. I don't know about Airbus so cannot comment, but I assume even Airbus without computer intervention follows the same laws sod physics.

Do correct me if I am wrong.

Keep the thread free of personal conflicts, lets try to present professional opinions without criticism. You all fly your aircraft, no need to play peacock here.
That said, I have noticed that members who easily jump into a discussion with the wrong answer (excess speed and always happy to point fingers at someone) find it very difficult to admit their mistake and keep being a part of the conversation in a more helpful way.
Sure nobody flies a heavy Boeing like a piston prop. Come on…..
worldrover is offline  
Old 25th Mar 2014, 17:51
  #63 (permalink)  
 
Join Date: Jan 2008
Location: ...
Posts: 3,753
Likes: 0
Received 0 Likes on 0 Posts
You're wrong! Its not that black and white. Either statement is correct.

I really don't see how this even matters. These statements are just a very simplified manner of teaching someone how to fly. The tricks of the jobs are learned through experience, and change per aircraft type, they can't be taught that easily.
737Jock is offline  
Old 25th Mar 2014, 21:58
  #64 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 2,167
Likes: 0
Received 1 Like on 1 Post
737jock---I think we agreed earlier that power + Atitude = Performance and that one will obviously effect the other.

Have you flown only the 737? Because I've flown both and can tell you that the 777 with its FBW will also maintain approx the same attitude if you change the thrust unlike non FBW Boeing's.

However be that as it may, Boeing and Airbus tech Pilots teach Pitch to control the profile and Thrust to control the speed followed by Pitch to Flare.

Both myself and Bloggs quoted the training manuals which are quite clear on the subject of pitch control during the flare and speed management on the approach.

Boeing and Airbus teach that during a manual approach they suggest the use of auto thrust ( or auto throttle ) to control the speed. This is the way it's done end if story full stop.

No amount of bull**** spewing from the crack pot Noodle will change that.

So what happens on an approach if you are on slope but 15 kts slow? 1/ you add thrust 2/ you maintain pitch attitude
That's what the manufacturer says to do and I don't see the point to do otherwise. Is noodle suggesting in that case he's going to push forward to regain the speed then increase thrust?does he think that's a good idea at low level? Because I don't think it is and neither do the manufacturers. Does he ever fly approaches manually with auto thrust? So why change techniques with or without auto thrust?

Don't get me started about his flare technique.......wow

Crazy people trying to re invent the damn wheel!!

Last edited by nitpicker330; 25th Mar 2014 at 22:15.
nitpicker330 is offline  
Old 25th Mar 2014, 22:18
  #65 (permalink)  
 
Join Date: Dec 2011
Location: upthere
Posts: 35
Likes: 0
Received 0 Likes on 0 Posts
nitpicker or Bloggs (I guess it is your alter ego…) Boeing suggests manual flight with Auto Throttle?

Even if it did, is this what we are discussing here?

Do you know how a wheel looks like buddy? Who is trying to reinvent what here?

There is no way you are flying anything heavier than a kite.
NoodleAir is offline  
Old 25th Mar 2014, 22:29
  #66 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 2,167
Likes: 0
Received 1 Like on 1 Post
Please tell me which Airline you "fly" for so I can avoid them.

You are a class one moron.

Now f off
nitpicker330 is offline  
Old 25th Mar 2014, 22:39
  #67 (permalink)  
 
Join Date: Dec 2011
Location: upthere
Posts: 35
Likes: 0
Received 0 Likes on 0 Posts
It is more than evident who is the moron.

By the way, misd-agin replied in avery nice way to your initial post.
Gave you a clue to help you understand how absurd is your theory.

You decided to reply in your typical way….. Most probably because you could not understand his comment. Standard reaction of a distressed ape.

You have 5 days till Sunday to learn how to fly your sim A330
NoodleAir is offline  
Old 25th Mar 2014, 22:46
  #68 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 2,167
Likes: 0
Received 1 Like on 1 Post
Congratulations Second officer Noodle you've made my ignore list
nitpicker330 is offline  
Old 25th Mar 2014, 23:11
  #69 (permalink)  
 
Join Date: Jan 2008
Location: ...
Posts: 3,753
Likes: 0
Received 0 Likes on 0 Posts
I have flown 737 and A320. Not 777 unfortunately, but in terms of discussion I think its better to leave the fancy computer bits out of it anyway.
But as you may remember from small aircraft during training, if you trim the aircraft for a speed in level flight and you add power, eventually you will end up climbing as the pitch attitude increases to maintain speed. This is obviously slower and likely less pronounced then the pitch up effect from underslung engines.

When someone is 15 kts slow I call go-around. No point trying to save that mess. But for the sake of the discussion I'll oblige.

Offcourse you need to add power and a lot of it as well since your on the back side of the powercurve. As the speed increases the pitch attitude reduces in order to maintain the path.
But what if you are so slow that you at a stall, you will lower the pitch attitude to reduce the aoa and thus increase airspeed. Only when that is under control you will slowly add power. Thats the new stall procedure according to the same manufacturers.

This example however has very little to do with a normal stabilized approach in windy or thermal conditions. And none of the manufacturers would advise us to get in a Vapp-15 situation.

The actual performance of the aircraft= pitch + power + external conditions (up/downdraft, gusts, tail/headwind etc)
The required performance is usually a 3 degree glidepath at Vapp.

As the external conditions vary you can only adjust pitch and power to match the actual performance of the aircraft to the required performance. As Vapp is fixed, pitch and power are linked. And it doesn't really matter which one is changed first.

Last edited by 737Jock; 25th Mar 2014 at 23:22.
737Jock is offline  
Old 25th Mar 2014, 23:19
  #70 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 2,167
Likes: 0
Received 1 Like on 1 Post
My 15 kts example may have been a touch excessive but certainly at around say 2000' you could get 7 to 10 kts below desired speed. Then it's the same, add thrust FIRST and not push forward first. The whole idea is that a Jet being swept wing is quite slippery and will accelerate nicely as a result of thrust application without needed to push the nose down. Simply pushing the nose down to regain the speed will result in a deviation below path and take a lot longer to accelerate. Thrust is a much more direct way of maintaining speed without flight path deviations.

Anyway my 2 bobs worth.
nitpicker330 is offline  
Old 25th Mar 2014, 23:32
  #71 (permalink)  
 
Join Date: Jan 2008
Location: ...
Posts: 3,753
Likes: 0
Received 0 Likes on 0 Posts
As said offcourse you add thrust, but thats only because you haven't been paying attention for a considerable amount of time during which you haven't been meeting the performance requirement for the last few seconds due to lack of thrust.

At 2000 feet i'm doing 160kts usually not anywhere near being low on my approach speed.

i'm talking about stabilized approaches as taught in the FCTM, not rescueing massive ****ups in this area.
737Jock is offline  
Old 25th Mar 2014, 23:43
  #72 (permalink)  
 
Join Date: Jun 2009
Location: Bedford, UK
Age: 70
Posts: 1,319
Received 24 Likes on 13 Posts
Bet the OP wished he never asked...
Mr Optimistic is offline  
Old 25th Mar 2014, 23:49
  #73 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 2,167
Likes: 0
Received 1 Like on 1 Post
Yes exactly at 2000' we will be gear down Flap 3 just about to select Flap full and be around 160 kts somewhere depending on ATC speed control requirements. A speed incursion below maneuver speed for that configuration isn't a hugh problem at that point as long as you correct immediately WITH THRUST.

Once again it was only an example I quoted above. Speed fluctuations as you know are caused by a myriad of things and not always the result of in-attention on the crews behalf!!

It's not unusual during gusty conditions to see + - 10 to 15kts during approach and this doesn't automatically require a go around if you are correcting ok.

In those conditions you will have bugged up anyway so being 10 kts below VRef ( VAPP ) isn't a problem as you are still way above VLS.

Airbus recommend ( as do Boeing ) use of Autothrust in managed mode for all manual approaches. Me? If it's gusty I actually prefer manual thrust in the 330 but on the 777 I always left it in. ( for reasons of ergonomics and design )
nitpicker330 is offline  
Old 26th Mar 2014, 00:00
  #74 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 2,167
Likes: 0
Received 1 Like on 1 Post
Besides. ATC often require 160kts to 4 DME on approach.
How does Noodle propose to slow down to a VREF of 135kts??
He says you use pitch for speed. So at 4 DME he raises the nose first does he? That would have the result of causing the aircraft to balloon high above the GS. Then he would have to quickly reduce thrust to get back down destabilizing his approach considerably. This is untidy and wrong practice. On Jets you don't want the nose to be pitching up or down on approach if you can help it, thrust is much more effective in facilitating speed changes whilst keeping a relative stable pitch attitude and thus flight path angle.

Handling the Big Jets 101.
nitpicker330 is offline  
Old 26th Mar 2014, 00:00
  #75 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,840
Received 2 Likes on 2 Posts
I think this discussion is becoming heated because we are talking about a specific situation, i.e. within seconds of the flight path intersecting with the ground.

In such a situation, we are relying much more on the short term effects of control inputs rather than the eventual steady state you would get in unaccelerated flight. This is a dynamic situation.

If you wish to reduce the rate of descent before touching down (a usual requirement), you need to apply a significant force for a period of time to the mass of the airframe such as to reduce the component of its velocity normal to the plane of the runway. How to do this in a jet aircraft...?

1) Add more thrust. As common airliners in a normal approach attitude have a thrust vector almost tangential to the surface, most of the applied force will go towards accelerating the airframe in the direction of flight. On an aircraft with underslung engines, a secondary effect will be a pitch-up moment but this will be mostly countered by the FBW on aircraft like the 777 and modern Airbuses. We are left with the other secondary effect of thrust, which is to increase the groundspeed over time (and hopefully the airspeed with it). The increase in lift generated from a few knots of extra airspeed (a few %) is not enough to significantly reduce the RoD during the time available before touchdown.

2) Increase the angle of attack. On a typical airfoil, the coefficient of lift could go up by c.25% for a c.3deg increase in AoA. This would result in a significant normal acceleration, reducing the RoD markedly over a short space of time.

On a non-FBW, low engined jet, applying thrust has the secondary effect of raising the nose, if not countered by the elevator. At this point the pilot has ceased to control the pitch through normal means and is relying on that secondary effect to provide an appropriate AoA to reduce the RoD. It is a technique but not one that I would recommend due to the extra delay in the feedback loop and the possibility of adding significant unwanted speed just before touchdown.

On the 777, adding more thrust just drives you faster towards where you were going before. Manual go-arounds often catch out people the first time when converting from conventional types as you have to deliberately pitch the aircraft positively into a go-around attitude after pressing TO/GA. Eventually, the 777 will pitch up of its own accord as the built in speed stability kicks in but it is a rather lengthy process and involves significant height loss before climbing.

I suppose the difference in the two methods near the ground is that by using pitch for RoD and power for airspeed, you are directly controlling all the important variables: the flightpath (touchdown point) and speed (runway used to stop). By relying on secondary effects, you may have to accept a significant deviation in one in order to make the other what you want.
FullWings is offline  
Old 26th Mar 2014, 00:25
  #76 (permalink)  
 
Join Date: Mar 2002
Location: Seat 1A
Posts: 8,556
Received 75 Likes on 43 Posts
Originally Posted by 737Jock
BTW if you make students do fake approaches and get them to fly level and add power as required you will miraculously find the flare pitch attitude. we are not bleeding off speed at all, we are reducing the rate of descent to zero and if you can fly level while the wheels touch the ground its called a greaser. And because we don't add power we lose speed which helps with reducing the landing distance.
This is becoming more irrational by the post. Fake approaches, flying level, adding power to find the pitch attitude? And then...we don't add power, we lose speed? I thought you said you use power to control PITCH? The reason you lose speed in the flare is because you pull the stick back to arrest the rate of descent.

When someone is 15 kts slow I call go-around. No point trying to save that mess. But for the sake of the discussion I'll oblige.

Offcourse you need to add power and a lot of it as well since your on the back side of the powercurve. As the speed increases the pitch attitude reduces in order to maintain the path.
So now we are using power to control (recover) the speed. Good. And how does the pitch attitude "reduce in order to maintain the path"? As the speed increases the pitch attitude will increase.

737Jock, We're not talking about Ref-15, nor stalling on the ILS, nor 160KIAS reducing at 2000ft, nor backside of the powercurve. Simple question: you get slow, say Vapp-5 or 10, you are on the glideslope. Please tell me you are not going to lower the nose to retrieve the speed. Please just put the power up! Whatever subsequently happens to the pitch, just use the stick to stay on the GS.

Originally Posted by Noodle
nitpicker or Bloggs (I guess it is your alter ego…) Boeing suggests manual flight with Auto Throttle?
Shock! Horror! Yes! Try it sometime; it works well. Not being a 737 driver, I understand though that it's not recommended in the 737 because of the amount of pitch-power coupling.

If you can't cope with the concept of manual flying with AT you probably shouldn't be in the cockpit.

I think happening here (and now that worldrover is here espousing the same heresy as Noodle and 737 jock) is that the pitch-power couple of the 737 is so powerful that you can, if low on slope, increase power and the nose will come up (just like a C150; trick flying). But if you get slow or fast whilst on-slope, I'll bet you don't lower the nose or pull the nose up (otherwise you'll obviously go off-slope). You adjust the power to get the speed back!

That is what picker and I are on about. Stick for slope/attitude control, power for speed control, just like the autopilot does it on an ILS.

Bet the OP wished he never asked...
Oh I don't know. It's been interesting reading how pilots fly aeroplanes. I see now the potential for overruns what with people advocating/using power to control the rate of descent at touchdown...

Fullwings: very well put. 737Jock and Noodle, I suggest you read Fullwing's post carefully. He has hit the nail on the head (after me and Nitpicker belted it first! )
Capn Bloggs is online now  
Old 26th Mar 2014, 03:31
  #77 (permalink)  

Bottums Up
 
Join Date: Feb 2000
Location: dunnunda
Age: 66
Posts: 3,440
Likes: 0
Received 1 Like on 1 Post
Noodle, Noodle, Noodle. Boy, did I open a can of worms back on page 1, or what?

Back when I learned to fly, circa 1983, I was taught pitch for speed on approach and power for RoD.

Then when I returned to the flying establishment as an instructor, mentored by a couple of excellent ex RAAF pilots, one the Chief Pilot, one the CFI, I had to teach their way, which was power for speed in all regimes of flight, and pitch for flight path. I didn't like it because it wasn't what I had been taught but as I didn't have any say in the policy I had to come to terms with it.

Coming to terms with this obvious heresy took only a very short time. It really made so much sense. I no longer had to think differently on approach as opposed to level flight, or climbing. In all phases of flight, and ground ops, if I want to go faster, I use more power, with a commensurate adjustment of pitch attitude to maintain the desired flight path.

BTW, your petulant smearing of Bloggs is so far wide of the mark, it reflects quite poorly on your own credibility. I can't comment on Nitpicker because I don't know him, whereas I've worked with Bloggs for close to 20 years, and even enjoyed his line training on my first jet.
Capt Claret is offline  
Old 26th Mar 2014, 04:13
  #78 (permalink)  
Thread Starter
 
Join Date: Dec 2005
Location: Above the Gay Bar
Posts: 109
Likes: 0
Received 0 Likes on 0 Posts
Wow…thanks for the GF1 brief on landing technique guys…I think I've got that covered!

My question, for the third time now, was to Airbus long course test pilots (NTPS, ETPS etc) and was asked to confirm my suspicion that hearing "RETARD" called 3 or 4 times during the flare is a symptom of incorrect technique.

I'm sure if we are all intelligent enough to register for a PPRUNE account, we are all aware that P + A = Perf, and that you adjust both P and A to correct MOMENTARY sink during the flare!

Anyway, assuming the odd useful comment will continue to be clouded by vitriol, I'll leave you guys to it!
luvmuhud is offline  
Old 26th Mar 2014, 04:29
  #79 (permalink)  
 
Join Date: Mar 2002
Location: Seat 1A
Posts: 8,556
Received 75 Likes on 43 Posts
Originally Posted by luvmuhud
My question, for the third time now...
Now Nitpicker isn't a test pilot AFAIK, but both his answers to your two previous posts clearly explain the scenario where keeping the thrust on during the flare would be appropriate.

What don't you understand about his answers?
Capn Bloggs is online now  
Old 26th Mar 2014, 05:20
  #80 (permalink)  
Thread Starter
 
Join Date: Dec 2005
Location: Above the Gay Bar
Posts: 109
Likes: 0
Received 0 Likes on 0 Posts
Right…this is DEFINITELY my last post…I promise!

No, he has explained that in the event of sink during very late finals, or during the initial part of the flare, that we control this with power (delayed thrust reduction) and attitude (slightly higher flare attitude). Ab-initio technique which is unquestionable.

If you hear RETARD 3-4 times during the flare, I suspect you have gone WAY beyond the requirement of avoiding a firm touchdown due sink, and are now confusing the aircraft and the rest of the crew! To quote Happy Gilmore's putting analogy…the aircraft wants to be on the ground…send it home…all you have to do is send it home. i.e…CLOSE THE FRICKIN' THRUST LEVERS!!!

(A mitigating factor for this seemingly less than ideal technique, is that my outfit is obsessed with touchdown zone…there is an impression on check rides that you must touchdown from 1000-2000' or face death…despite crossing the threshold at 50' and using correct technique but then prevailing wind conditions 'flying' you slightly outside this area)
luvmuhud is offline  


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.