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Thread: My default CRJ700 flies with a nose-down attitude

  1. Default

    Hello folks

    Following on from your advice I have just flown the CRJ700 and A321 at 300 kts Indicated and they both still fly with a nose-down attitude. The other aircraft all fly horizontally.

    I have not tried moving the payload but will give that a go later today.
    As for fuel, I have it set to unlimited.

    Kind regards

    Frank C

  2. Default

    Hello again everyone

    I have been taking in the advice and experimenting, flying the CRJ700 from 300 indicated, gradually taking off the throttles and the nose-down attitude gradually levelled out between 260 - 250 indicated.

    I only flew at 3,000' with the weather custom set to clear skies and no wind.

    Kind regards

    Frank C

  3. Default

    This is in response to user DownWind66's questions.
    -------------

    When the air moves faster over the wings, the result is more lift.
    The consequence is that to stay at the same altitude, the plane requires less pitch up. (pitching up results in more lift. pitching down in less.)

    When increasing speed, if you don't reduce the pitch, the plane would climb.
    Ways to pitch down would be:
    -1- push the joystick forward/yoke in, and hold it there from then on.
    -2- trim down the elevator.
    (In manual flight you would use the yoke while accelerating. And when the new higher speed is reached, you would start adding trim while at the same time bringing the toke/joystick back to the neutral position.)

    -or, -3- you let the autopilot keep you at the same altitude. The autopilot only uses the elevator trim to pitch down. It does not use the yoke.

    -----
    The net result:
    increasing the speed while you stick to the same altitude, the pitch of the aircraft will reduce. Sometimes even going to negative pitch.

    ----------
    All these planes, the 737, a321, crj700, and 747
    have a maximum airspeed of around 345 knots.
    The maximum airspeed is the highest speed a plane can safely reach. Fly faster, and the plane will start to break apart.
    It is a limit you should not exceed. (it is possible to fly too fast and have your plane fall apart. Be careful.)
    The limit for each plane can be found in the information pages on the kneeboard. The kneeboard can be viewed while you are flying in fsx.

    Why not exceed it? long story.
    Action = - reaction.
    If you bump into a wall at 10 Mph, it hurts. If the wall bumps into you at 10 knots, it hurts the same.
    Let's say it's a calm day, no wind. No air movement.
    Let's say your fly at 300Kt. the air may be standing still, but you are hitting it at 300 kt.
    So if you would stick your hand out the window, you would feel the rushing past. At 300Kt.
    With your hand sticking out a small hole like that, getting hit by air at 300Kt, your hand would get clean ripped of. The pressure the air exerts on your hand would be enormous.

    This same pressure is experienced by every part of the plane. The windshield, the wings, the engines, the tail, everything. Also by the front facing pitot tubes.
    This results in air pressure inside those front facing pitot tubes. This pitot tube air pressure is shown in your cockpit. As Airspeed. Indicated Airspeed. (you don't see 25 psi, you see 250 knots. [25 and 250 are not real world actual values, this is just as example.])
    As I said. Indicated Airspeed. Also known as IAS.

    This means that the IAS you see on your Cockpit gauges are a direct result of Air Pressure created by the wind hitting the plane.
    If this wind speed gets too high, parts will start blowing off the aircraft. body panels rip of the top of the plane, the tail gets torn apart, all control is lost and the plane breaks up completely.
    So keep IAS below Max Airspeed given in the kneeboard.

    --
    Weather.
    Between a high and a low pressure weather area, you often have an area where two layers of air flow in opposite directions to each other. Not above each other, but next to each other.
    Like so:
    East
    -high pressure area-->> South
    <<-low pressure area- South
    West

    In the west is a Low, with wind flowing Northward. And in the East is a High, with wind flowing South.
    If you are flying from Southwest to Northeast, you will cross the line, and go from an area with maybe a 20 knot tailwind to an area with a maybe 25 knot headwind.

    You might think there is a wide mixing area where wind is almost neutral. But this is not the case. Usually one air-layer has more moisture then the other. And is also colder. And air layers of different temperatures do not mix easily. So the transition from tailwind to headwind will be very abrupt. Very sudden.

    Now why would that matter?
    That matters because you are always flying in an air layer.
    Let's say you have a 20 knot tailwind. your IAS is 300kt.
    In other words the air-layer you are in is moving in the same direction you are traveling in. And you are going so fast that you still feel a 300 knot pressure on the windscreen.

    So even though the wind is moving the air away from you, you are "overtaking" it with a speed that is 300knot faster then that wind is moving away from you.
    Now the tailwind suddenly drops away. In other words "the air-layer around you no longer moves away from you".
    The plane is a heavy thing, it doesn't stop on a dime, it has loads of momentum. So it keeps traveling forward at the same speed in relation to the ground.
    But the air around the plane no longer move as. So now the air hits the windscreen of the plane with 20 knots more speed.
    And the pitot tubes, the tail, the engines, and the wings.
    pitot tubes: IAS will now of course indicate 20 knots more. 320 instead of 300
    Wings: flying at 320 knots instead of 300 results in more lift.
    Autopilot: trims down to stay at same altitude. Because the extra lift is making the plane pitch up and climb.
    Throttles: will spool back to reduce speed back to the 300 that is still set on the autothrottle.

    However, many of these systems are slow to respond. It takes some time to slow down. Autopilot responds relatively fast, but throttles take time to spool down, and the plane is simply so heavy it takes some time before it slows.

    ----------
    That's just with a 20 knot tailwind dropping away.
    But if the 20 knot tailwind is replaced by a headwind of 20 knots, the combined effect is an increase in IAS of 40 knots.

    If at that time you are very close to maximum airspeed, you have a big problem.
    One moment you are flying along at 340 knots, just 10 knots below max indicated airspeed, the next moment you are doing 380 knots, 30 knots above max airspeed.

    You can't slow down by disengaging autopilot and pulling the yoke to pitch up quickly. Pulling up, the change in elevator position would put so much force on the elevator and tail construction it could easily shear off.


    Conclusion/summary:
    Know the maximum Indicated AirSpeed IAS of the plane you are flying.
    Stay well below it.
    Pitch will be lower at higher IAS. (in any given situation, not just in level flight.)
    When checking the pitch on the PFD (Primary Flight Display) in the cockpit, if pitch looks abnormally low for the situation, check if your Indicated Air Speed is not too high.
    Be aware wind shifts can occur. Tailwinds can turn to headwinds, increasing your IAS very suddenly.



    ----
    last remarks
    The allowed Maximum Indicated Airspeed is lower when the flaps are extended. There is a Max Flap Speed for every flap setting. (More flaps set--lower max speed allowed.)
    There is also a speed limit for flying with landing gear extended.
    And a speed limit above which you may not extend or retract the gear.
    Last edited by il88pp; 05-17-2018 at 10:12 AM.

  4. #14
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    Default

    ##### il88pp ##### - You say "In response to Downwind66"s questions...." I had no questions of you or anyone else on this subject, connolly44 is the OP for this thread! I don't fly at these airspeeds or at high altitudes, and I have never had issues with either the CRJ700 or the A321. Not being disrespectful towards you, I am not reading your short story either, as my mind has enough in it without adding to it! Maybe, Frank, the OP has time to read it, I do not!

    Rick

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    Default

    Quote Originally Posted by connolly44 View Post
    Hello again everyone

    I have been taking in the advice and experimenting, flying the CRJ700 from 300 indicated, gradually taking off the throttles and the nose-down attitude gradually levelled out between 260 - 250 indicated.

    I only flew at 3,000' with the weather custom set to clear skies and no wind.

    Kind regards

    Frank C
    Frank - Glad to hear that! Same results with the A321?

    Have a nice day! - Rick

  6. Default

    Downwind66,
    You said in your post you weren't sure Why increased speed would cause lower speed. So I set out to explain that to you.
    I decided to stick on a lot of extra info.
    Not because it was needed, but because it is good to have the whole story.

    To fully understand, a simple "speed up means pitch goes down" is not enough. There needs to be (a lot of) context.
    On when this happens, why this happens, and how it happens.

    I do not see how you saw my text as criticism.
    My text was only there to provide information. No criticism meant at all.
    il.

  7. Default

    Sorry. I see I misread your post. You did indeed not (need to) ask.

    Nevermind. As I already said, no criticism was intended.

  8. #18
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    Default

    Quote Originally Posted by il88pp View Post
    Sorry. I see I misread your post. You did indeed not (need to) ask.

    Nevermind. As I already said, no criticism was intended.
    Not a problem, and I did not take it as criticism, I just wanted to let you know who the person in need was and it wasn't me! I did, in fact, agree with you that 400 KIAS was about 100 knots too fast. The fastest speed I have set on either the CRJ700 and/or A321 is 310 KIAS, and have not had issues myself!

    Thanks il !! Rick

  9. Default

    Quote Originally Posted by connolly44 View Post
    Hello folks

    Following on from your advice I have just flown the CRJ700 and A321 at 300 kts Indicated and they both still fly with a nose-down attitude. The other aircraft all fly horizontally.

    I have not tried moving the payload but will give that a go later today.
    As for fuel, I have it set to unlimited.

    Kind regards

    Frank C
    Some submarine movies always have the crew running forward when they need to make a fast dive to get away from the depth charges.

    I though maybe moving passengers rearward would nose the plane up a bit, but it didn't seem to have much of a noticeable effect.
    Gigabyte GA-X99 Gaming G1, i7-5960X, Noctua NH-D14, Crucial Ballistix Elite 64gb 2666, Nvidia GTX Titan X, Creative ZxR, WD VelociRaptor 250gb and 1000gb, Sony BDU-X10S BD-ROM, PC Power & Cooling 1200w, CM Cosmos S, Logitech M570/K800 Wireless Trackball/Keyboard, Windows 7 64 Ultimate

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    Default

    I just did a flight with the CRJ700 from KSFO-KPSP. Cruise altitude was at FTL330, KIAS at280, MACH=.78 and Ground Speed of 502 Knots. It does show slightly nose-down. I am using A/P.

    I found even sitting on the ground, the same nose-down angle.

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