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ingoke

Flying technique - how is it done in real life?

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Hi folks,

I have a short question to real pilots: During take off and after landing I have to push the joystick in the FBW Airbus forward to keep the aircraft on the ground and to be able to stabilize the aircraft by using the pedals. Does it work that way in real life, too? 

Thanks for your answers.

Ingo 

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In very short NO.

Typical problem regarding flight aerodynamics with ASOBO, all their airplanes suffer from unrealistic flight characteristics.


I9- 13900K- CPU @ 5.0GHz, 64 GB RAM @ 6200MHz, NVIDIA RTX 4090

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In general, it's typical to add some slight forward pressure. The reason we do it is because the nose may lift when hitting humps and bumps along the runway. This will assist with rudder pedal steering and keeps the nose from lifting and slamming once you come on the brakes. In some aircraft, the spoilers may cause some pitch up, but again, slight forward pressure will keep it down.

 

Rick

Edited by G550flyer
omisssion
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Well, two different answers. 😂 But I have to admit that Rick´s answer is plausible. Thanks for your time!

Ingo

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There is some truth  in Ricks answer.

But the question was related to the Airbus which is quite balanced in reference to the CG position. The airplanes with AFT CG most likely will require a slight forward pressure in certain conditions.

Now regarding the rwy bumps it's kind of the stretch, but again is subject to interpretation. I never ever encountered a nose lift off a rwy do to rough surfaces unless is a pilot technical error.

Edited by killthespam

I9- 13900K- CPU @ 5.0GHz, 64 GB RAM @ 6200MHz, NVIDIA RTX 4090

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15 minutes ago, ingoke said:

Well, two different answers. 😂 But I have to admit that Rick´s answer is plausible. Thanks for your time!

Anytime, you never think about it until you do it real world. You have probably noticed while on airliners how the plane bounces and hops around on takeoff and landing roll. When I was flying DC10s, the nose would pitch up on landing when the ground spoilers went to the 2/3 position. They would not go to full until the nose strut was compressed. That compression also unlock the number 2(tail) thrust reverser idle interlock. In that jet, not only did you want the nose firmly on the ground for rudder pedal nose steering, it also controlled the ground sensing mechanism which was on the nose strut. That system would put you in air or ground mode.

Rick 

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Here is your answer regarding A320 in video below I found on youtube. However, as FBW user I can tell I have never had to push stick forward during take off roll or after landing. I fly different configs, but I make sure CG is always in place. As far as I know IRL some aircraft required to push stick down. I certainly didn't fly those as light GA flyer, but when I was doing training in Level D An-124 sim I've been told to push stick down until Vr by instructor.

https://www.youtube.com/watch?v=8YaQch_y9DA

Edited by sd_flyer

flight sim addict, airplane owner, CFI

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10 minutes ago, killthespam said:

Now regarding the rwy bumps it's kind of the stretch, but again is subject to interpretation. I never ever encountered a nose lift off a rwy do to rough surfaces unless is a pilot technical error.

You must have not flown into some of the places I have. Aircraft are trimmed to naturally seek an attitude that would attain V2 naturally. It also provides the desirable rotation rate. This is why in traditional aircraft, you are trimming nose down after lift off because you are V2+10(all engines) and the nose wants to rise as you are 10 kts past the trimmed V2 speed. From my USAF days to my corporate life, I have flown to airports all over the world. All runways are not level and smooth. At the speeds involved, it doesn't take much of a Bump or Hump to make the nose strut decompress or lift. Moscow has a runway with a big hump in the middle. During takeoff at night in heavy rain once, I received a weight on wheels and ground spoiler warning after hitting that hump. The aircraft lifted enough off the struts to trigger a momentary airborne signal though we never left the ground. It also flagged the ground spoilers because they did not deploy confusing the system. So I got a triple bong warning, master warning and CAS message. I glanced at the flight control indicator on my PFD and stated continuing. Imagine if I had not had slight forward pressure on the yoke. This was not pilot error and I have seen some humpy runways which gets interesting when landing on them. As for MSFS2020, we all know that the flight model is not solid.

By the way, in all of the AFMs and operating manuals of the "real world aircraft" I have flown, the takeoff/landing roll section of normal procedures state "slight forward pressure", I didn't just make it up.

Rick   

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41 minutes ago, killthespam said:

Now regarding the rwy bumps it's kind of the stretch, but again is subject to interpretation. I never ever encountered a nose lift off a rwy do to rough surfaces unless is a pilot technical error.

This is from the A318/320/321 FCTM as I have never flown scare buses.

Once the thrust is set, the PF announces the indications on the FMA. The PNF must
check that the thrust is set by 80 kt and must announce ”Thrust Set”.
The Captain must keep his hand on the thrust levers when the thrust levers are set to
TOGA/FLX notch and until V1.
On a normal takeoff, to counteract the pitch up moment during thrust application, the
PF should apply half forward (full forward in cross wind case) sidestick at the start of
the takeoff roll until reaching 80 kt. At this point, the input should be gradually reduced

For landing

When the aircraft is on the ground, pitch and roll control operates in Direct Law.
Consequently, when the aircraft touches down, the pilot flies the nose down
conventionally, varying sidestick input as required, to control the derotation rate.
After touch down, when reverse thrust is selected (on at least one engine) and one main
landing gear strut is compressed, the ground spoilers partially extend to establish ground
contact. The ground spoilers fully extend when both main landing gears are compressed.
A small nose down term on the elevators is introduced by the control law, which
compensates the pitch up tendency with ground spoiler extension.
It is not recommended to keep the nose high in order to increase aircraft drag during the
initial part of the roll-out, as this technique is inefficient and increases the risk of tail
strike. Furthermore, if auto brake MED is used, it may lead to a hard nose gear touch
down.

Edited by G550flyer
omission
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I have not flown IRL in an awfully long time but my recollection for GA  was you would only ever taxi or start the takeoff roll with back stick if you had a serious head wind which would try and lift your tail or it was a very rough runway and you were trying to avoid a prop strike.

The rule of thumb was "climb into a headwind dive away from a tail wind".

Edited by Glenn Fitzpatrick

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Rick,
 
Similar experience here + civilian.
We had the -30 and -40 and yes they are known for AFT CG and having issues, even the MD11.
Now in total honesty, I never flew those but I had issues with the pilots transitioning to the 400 from the -30 and -40 where right away on t.o. roll and landing will bury the nosewheel.
I guess that airplane did an impression on you guys.
This "slight forward pressure" is a military thing that I suffered for a long time, on the 747s and A380 in flight training manuals there is no mentioning of that. 
Now I acknowledge that some airlines have different procedures, funny enough is that where you will find some ex-military guys involved in the training department will try to do what they were used to and push hard on certain items that have no place in the civilian world. Lucky enough this doesn't happen anymore to have a civilian airline suffocated with military procedures.
Regarding Airbus, obviously, you don't fly it and for some reason, the statements are not quite correct regarding the FCL.
You say that "When the aircraft is on the ground, pitch and roll control operates in Direct Law".
First, DIRECT LAW, is the lowest level of computer flight control and occurs with certain failures.
After landing, NORMAL LAW (normal operating configuration of the systems) will enter in Ground mode where there is a proportional relationship between sidestick deflection and deflection of the flight controls and when activated will reset stab trim to zero.
 
 Now regarding "Consequently, when the aircraft touches down, the pilot flies the nose down conventionally".
 
Unfortunately not correct in the Airbus, under NORMAL LAW FLARE MODE, the transition to flare mode occurs at 50 FT RA where the system memorizes pitch attitude and progressively reduces pitch forcing the pilot to flare the aircraft, slightly back pressure on the stick, and neutral after a touchdown or some corrections on aileron for the x-wind.
 
This scenario you describing must be really extreme that "On a normal takeoff, to counteract the pitch up moment during thrust application, this is a perfect example of wrong power setting or an out off CG situation. 
Yes, there are recommendations in certain x-wind conditions to maintain directional control you might need to apply full forward column (stick) position but not under a normal t.o. situation to prevent pitch up moments.
 
For the nonbelievers 
 
 
Enough said!
Edited by killthespam

I9- 13900K- CPU @ 5.0GHz, 64 GB RAM @ 6200MHz, NVIDIA RTX 4090

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7 minutes ago, killthespam said:

military thing

Whoa there. It is a USAF AMC thing. 

 

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I think some of the tendency for the nose to rise prematurely on some MSFS aircraft during takeoff is due to the ground effect characteristic being too strong in the flight model. 

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Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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3 hours ago, killthespam said:
I guess that airplane did an impression on you guys.
This "slight forward pressure" is a military thing that I suffered for a long time, on the 747s and A380 in flight training manuals there is no mentioning of that. 
Now I acknowledge that some airlines have different procedures, funny enough is that where you will find some ex-military guys involved in the training department will try to do what they were used to and push hard on certain items that have no place in the civilian world. Lucky enough this doesn't happen anymore to have a civilian airline suffocated with military procedures.

I don't know if this is an attempt to slight military pilots or what. For the most part, with my military experience(USAF), military peeps are sticklers for regulations, procedures and SOPs. No one that I have known or seen with military experience have pushed agendas at all. We learn the AFM, procedures and SOPs and apply them. What you find in military pilots is a wealth of experience operating in different environments, high situational awareness, world wide experience and a high level of professionalism. It's a mindset. A lot of this is gained because we do more than just point A to point B. During my last year of service we were highly sought after. Ok, back on topic. You mentioned "slight forward pressure" is a military thing. Here is an excerpt from the 747 FCTM that you mentioned above.

    Light forward pressure is held on the control column. Keep the airplane on
centerline with rudder pedal steering and rudder. The rudder becomes effective
between 40 and 60 knots. Maximum nose wheel steering effectiveness is available
when above taxi speeds by using rudder pedal steering.

Interestingly enough, the 757/767 manual has the same verbiage in it's FCTM as well.

MD80

  Pilot Flying
• The pilot flying should gradually relax forward pressure on the control
column, so as to arrive at VR prepared to rotate.

777

Rotation and Liftoff
As the airspeed approaches V1, the slight forward control column pressure is
relaxed to neutral, allowing for a smooth rotation to begin at VR. Takeoff and
initial climb performance depend on rotating at the correct airspeed and proper
rate, to the rotation target attitude. Early, rapid, or over-rotation may cause aft
fuselage contact with the runway. Late, slow, or under-rotation increases
takeoff ground roll. Any improper rotation decreases initial climb performance.
Aft fuselage contact occurs at a pitch attitude of 12 degrees with wheels on the
runway and landing gear struts extended.

In reality, anyone here can look this up for verification as long as they have a AOM or FCTM. It's a pain to post images here so I just pasted the info here. This is just to show that what I mentioned earlier is not a military thing as was described, it's a aircraft thing. Actually, you never even think about it because it's not a lot of pressure, your hand is resting against the yoke. As usual, my aim is to bring real world ops to those who don't have the opportunity to perform them. After all, I started in flightsim. I am not here to slight people or communities. I am not here to miss inform either, we have enough of that going on as it is. When I first took over flight standards, I told each new evaluator, we don't make it up, we look it up. Have a nice day and fly safe.

Rick 

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Also do not forget that in reality the aircraft while on the ground tends to be more "nose down" than while flying in free air due to the downwash of the wings getting inhibited due to the ground.

In free flight, the air will move "downwards" behind the wings, due to the way they create lift.

This downwash will help "push down" the elevator (increasing their effectiveness), which in turn keeps the nose up.

While on the runway, the air can not flow down, because the runway blocks it. Thats why the plane - even though it is trimmed for V2+15 approximately - tends to keep its nose on the runway until the pilot actively pulls it up.

This effect varies from aircraft to aircraft due to varying geometry (it might be completely missing on a T-tail, for example).

Also keep in mind that often the take-off trim (while set for V2+15) does not account for thrust reduction during take-off (TASS or FLEX), which in turn reduces the nose-up momentum. Therefore the pilot needs to pull up "even more" when heavily reducing take-off thrust.

A last word on the NEO: The real plane I fly features a "tailstrike protection". The ELACs will feed in a "nose down" effect until safely off of the runway to help against "overrotation" which might result in a tailstrike. Yet another reason to hate flying the A320 😉. At 50 feet or so this effect stops and the plane will tend to "jump" noseup if you don´t anticpate it.

So next time you fly on a NEO and feel as if the pilot is a little rough on the elevator during liftoff...be lenient.

Cheers, Jan

 

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