Jump to content

Sign in to follow this  
Guest dynastykid22

747 pitch attitude

Recommended Posts

Guest dynastykid22

hello fellow pilots, Hopefully this isnt an ignorant question, but i have searched the forums and have found no answers so i caome to you guys for the answers....hope that makes sense. but anyways, when i fly the 747-400/400F, when I am on descent and bleed off speed to get into landing config., my pitch up attitude goes from 0-2.5 degrees nose up to about 5-8 degrees nose up. this happens when my speed drops into the flap schedule...the nose starts to pitch up from 2.5 to 8 degrees nose up when I go from flaps up to flaps 20. After i set flaps 20, the plane starts to pitch down to about 2.5 degrees nose up attitude where I finnaly set my flaps to 30 and i end up in landing config. my question is this......................... Am i doing anything wrong and is that why the plane pitches up during deployment of flaps from 0-20 degrees of flaps....or is it natural for the plane to do that. If im doing anything wrong then can you guys fill me in how to keep my noes downn?BTW....I fly the autopilot till im established on the LOC...im at about 210KIAS and then i let the autopilot fly the approach until im at 2500 feet then i take over. I also deploy flaps in this manner.....when it passes through UP, i go flap 1...when it passes through 1....i go flap 5 and so on.if you guys could enlighten me on how you guys fly the plane that would be appriciated..thank you :)-Matt Kubanda

Share this post


Link to post
Guest D17S

That's all entirely normal. Ive been working through the dynamic of a had flown approach too. You've probably noticed that as the airplane pitches up as the flaps extend, it also tends to float above GS. Once you have initially established on GS, notice your rate of decent will be 800 fpm. (Check your chart. The exact GS/ROD number is published there). Use the VS indicator as your "Early Warning System" for GS deviation. If you see 900 FPM, you will be off glideslope very shortly. Adjust your VS back to 800 FPM BeFore the dot wanders off. I always try to use pitch trim to setup neutral control column pressure (i.e., none) while maintaining 800 FPM and dot-on at initial GS capture. This works great, until it comes time for that next notch of flaps . . . then it all goes whacko. As the flaps extend to the next notch, the nose pitches up and the airplane starts to drift up. Watch your ROD start to float up to 700-600 FPM. Then, before you know it, you're dot high. Dang, what's a pilot to do? Trim! I finally set up flaps and pitch trim on the same hat switch. As soon as I pull in another notch of flaps, I immediately start feathering in nose down trim. Don't wait for rate to start floating. So far, this is far from perfected, but I think this might be what a real pilot does. If you have ever watched a real approach from over a Captain's shoulder, that left thumb (his trimmin' digit using those pitch-trim pickle switches) sure is busy. I think I've discovered why. I think this is might be called airmanship, but I just like to - NoT crash.

Share this post


Link to post

Similar pitch-ups occur when you fly a Cessna 172. You can be a bit more aggressive by pushing on the control column to counteract such pitch excursions. You could also watch how a fully coupled autopilot approach looks like (flying both LOC and GS) and try to imitate it when you fly manually.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg


Michael J.

Share this post


Link to post

Perfect timing! I just finished a B744 flight. I too find that the nose pitches up at first. I think it is natural for this to happen due to the change in the wing's configuration. I think the reason why you may not notice it in real life is because the pilots descend at a rate that requires the nose to remain at a low attitude.As far as why the nose is pitched up so high is probably due to the leading edge flaps. Now, I'm no expert, but the leading edge flaps being fully extended basically lowers the front edge of the wing. The trailing edge flaps however are still up. As the trailing edge flaps come down to 25 degrees, it matches the lowered leading edge flap and the nose comes back down.For my approach procedures, I'm usually below 190kts as ATC vector me toward final. Then, I arm LOC if I'm not flying a visual approach. I will leave my autothrottle connected however. Just before the A/P captures the localiser, I drop my flaps to 20 and drop the gear. I went through 1, 5, and 10 earlier during my decent to final and to help slow down. I usually drop my flaps before schedule early on since I'm trying to slow down. Usually when I'm well established on final I drop to my landing flaps; either 25 or 30 degrees.Since I'm below the glide slope at first, I'll arm approach just as my G/S bug starts to move. I'll disconnect my autopilot just before Decision Altitude if it's still connected and I'm not on a CAT3 and disconnect my autothrottle at about 150-100 feet. Between "100" and "50" my throttles go to idle depending on how close I am to my VREF. Once I hit VREF, I begin my flare and hope I don't balloon or touch down too hard.Just as my own question, how do you achieve idle reverse in FS? Do I just hit F2 once instead of hold it down?EDIT: Gee, no one posted when I started.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

Share this post


Link to post

<I'm not sure there is such a thing in FS. Hitting F2 just once keeps the REV thrust going (it times out on it's own, maybe that's Idle REV). 'Course, F1 stows the reverse and returns to idle.The change in pitch due to flaps is primarily due to the center of lift moving aft as flaps deploy. The C414 I fly does this even tho they are split flaps (no surface moves rearward).


Dan Downs KCRP

Share this post


Link to post

>I'm not sure there is such a thing in FS. Hitting F2 just once>keeps the REV thrust going (it times out on it's own, maybe>that's Idle REV). 'Course, F1 stows the reverse and returns to>idle.Thanks. It works for Concorde but only on the ground. It's tricky to get the reverser's open in the air. I thought it might work but never got around to trying it with any other aircraft. Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

Share this post


Link to post

Hi Matt and all others,I think Matt wants to say a complete different story :All has to do with AOA or "angle of attack".As you bleed off speed (and stay at the same level) the nose will pitch up to prevent descending.If you go to far in bleeding off speed you go into a stall ... unless you start deploying flaps.And now it comes (at least this is how i understand it):The flap indications on the PFD is the MINIMUM speed at witch you have to set the flap, if not you risk to going into a stall!So this means that you can safely go to the next flap setting even if you don't past the speed marking for that flap setting (what an explanation:D ).You just have to see that you don't set next flap before you pass the minimum safe speed for that flap setting, and these minimums are indicated on the panel next to the upper eicas CRT.So, i hope i was a little bit correct and helpfull.If not, please let some more professional captain explain it in more dept and with more precise (and with less faults in there language...)


Regards,

William Vrielynck

Share this post


Link to post
Guest D17S

There's this thing called "Center of Lift" (CL) too. There's a longitudinal (fore/aft) point on the wing where a maximum pressure differential exists. Maximum differential? What? As you know, the airfoil create a low pressure area on top of the wing that acts to move the wing toward it. But this pressure is only "low" relative to the high(er) pressure area on the bottom of the wing. One could say the wing is lifted. But just as accurately, one could say the wing is pushed into the upper wing's low pressure area buy the lower wing's high pressure area. Did you know that a lot of horizontal stabilizers use an upside down airfoil? Up and down don't matter to this dynamic any more than north and south matter to a the Santa Anna winds moving from a high(er) pressure desert to a low(er) pressure valley. Whatever's there (stray cats, or 747 wings) will move from high pressure area to the low pressure area.The center of Lift is where this maximum differential occurs. Schematically, it's like a string that suspends the airplane. But there's more to it. There's weight. This has a center point too, called the Center of Gravity (CG). Schematically this can be considered a fulcrum. The airplane is balanced on this fulcrum.The Center of Lift moves back and forth on the wing relative to airspeed and the flap position (And a lot of other things too). For our approach scenario, the Center of Gravity stays fixed. If CL is exactly over the CG, the airplane flys "flat." As we move the flaps down, the center of lift (generally) moves forward and the nose pitches up. As we speed up the CL will also move forward and pitch the nose up. It all works in reverse too. (Note this is a schematic representation. There's even more to it than this. These are just basic concepts)The pitch changes then (in turn) effect our rate of descent and airspeed. This is why it's such a constant adjusting act to keep the airplane on GS during descent. I've found the trick is to anticipate what the airplane is going to do before it does it. If I"m good, my pitch trim inputs will exactly counteract the CL movements that are occurring. To an observer (aka passengers. . . . ahhh, and ATC?), it will seem as if nothing is happening at all. I am locked onto that glideslope. This appears to be quite a skill. I still have a ways to go.

Share this post


Link to post

>The center of Lift is where this maximum differential occurs.Sam,The above statment is not true. Ceneter of Lift has no relation to where the maximum pressure differential occurs. It is rather the place where you could place the vector of the total lift and obtain correct moment of this force in relation to the rest of aircraft. In other words it is the result of summation (integration) of tiny lift forces across the whole wing and translating it into a single place on the wing. For practical pilots this may not be such an important remark but I just did not want folks here to take the above sentence at its face value.The wikepedia has the correct definition: An aircraft's center of lift is the location at which the net lift produced by all airfoils is located.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg


Michael J.

Share this post


Link to post

>The flap indications on the PFD is the MINIMUM speed at witch>you have to set the flap, if not you risk to going into a>stall!The flap indications are the recommended deployment schedule to drop the flaps yet still maintain efficient flight. You can actually drop the speed below the flap indications without stalling. It's the yellow line in the speed tape that indicates the minimum speed before you risk a stall and the red bricks pretty much means that you just entered a stall.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

Share this post


Link to post
Guest D17S

Darn, is it next week already? Knew it wouldn't take long.

Share this post


Link to post

>>The flap indications on the PFD is the MINIMUM speed at>witch>>you have to set the flap, if not you risk to going into a>>stall!>>The flap indications are the recommended deployment schedule>to drop the flaps yet still maintain efficient flight. You>can actually drop the speed below the flap indications without>stalling. It's the yellow line in the speed tape that>indicates the minimum speed before you risk a stall and the>red bricks pretty much means that you just entered a stall.>>Ryan Gamurot>Lucky to live Hawai'i>>http://www.virtualpilots.org/signatures/vpa296.pngHi Ryan, Thanks for the update:-roll


Regards,

William Vrielynck

Share this post


Link to post

The PFD flap indications are the Minimum manouvering speed for that flap setting. The flaps can be dropped anywhere from the placarded speed to the min mav speed,but you should not allow your airspeed to fall below Min Mav speed untill you have the next flap setting indicating green.Jon

Share this post


Link to post
Guest yhfok

One should be careful NOT to fly the aircraft with trim, whether it is a C172 or a B744. Using the control column to adjust for pitch changes and to maintain a desired performance should never be considered as "agressive" -- it is the only proper way to fly the aircraft.Remember the rules of thumb from the first PPL flight lessons:1. Climb: APT2. Cruise: APT3. Descent: PAT (remember down PAT)4. Leveling off from Climb/Descent: APTA = Attitude, P = Power, T = TrimNote that the pressure in the control column is only to be trimmed out when the desired performance is attained. If you want performance to remain constant, any changes in aircraft configuration (i.e. flaps, gear) or in power requires changes in attitude and the aircraft to be re-trimmed. Recall the formula Attitude + Power = Performance.Also, never chase the instruments, especially the VSI since it is the instrument that lags the most. Rather, fly the numbers. Set an attitude and a power setting that you know by experience will produce the desired performance, scan the instruments to gauge the performance, and make small adjustments if necessary.Watching the AP is a bad way to learn proper flying since the trim is in constant movement due to the AP logic.Never ever fly the aircraft with trim!!Best regards,Sunny Y. H. Fok

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    2%
    $540.00 of $25,000.00 Donate Now
×
×
  • Create New...