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+--- Thread: strange flight controls <100ft (/showthread.php?tid=11844)
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strange flight controls <100ft - adrian8891 - 19-06-2015
Hello all,
I don't know what is going on (maybe because im not a real pilot...But i wish to :D) when Im approaching to land.
I use ILS landing with App On, at 800-600ft I disable autopilot and throttle control. From this moment I fly on manual Controls.
Everything seems to be great, I'm at good glidescope and seems smooth landing!
At around minimums (100-150ft) strange thing is going on. Seems that something is unlocking (?) and plane goes suddenly down
on nose. It causes that I have to pull up nose dramatically and it almost causes crash or At least very hard landing.
Does anyone know what is all about?
I'm flying only default Airbus A321.
Re: strange flight controls <100ft - Leftcoaster - 19-06-2015
Curious... If you're description is accurate this seems counter-intuitive but here's some wild-a$$ guesses anyway.
At about 100-150 feet above ground level FS9 (and presumably FSX as well) simulates ground effect. This causes an increase in lift that often leads to a minor pitch up
rather than pitch down. However, depending on what weather model you're using I believe that the low-level winds kick in at about the same height. Wind
direction/velocity change could explain a rapid pitch down even without windshear conditions. To be honest I am unsure if any FS version models low-level
windshear accurately.
You may be coming in too fast as an increase in lift at high speeds might pitch the nose down as the wing immediately tries to achieve the correct pitch for your current
configuration and velocity. Typically though, the result of additional lift is a pitch up followed by loss of airspeed. The theory is that at low speed the wings tend to pitch
up to increase lift but at high speeds increased lift causes the wing tends to pitch down, forcing the nose down and increasing drag. In any event, something external
seems to be disrupting your trim, which might indicate an energy state problem on final approach.
I know next to nothing specific about the Airbus A321 in FS but landing anything is far easier if you nail the correct Vat (minimum speed crossing the runway
Threshold) or Vref (Reference Landing Speed) for your current weight and configuration. This info should be available from your FMC.
Minor terminology points: altitude Minimums is the altitude (generally expressed as height above the runway threshold) at which point you are required to have the
runway in sight. This varies by airport and may be anywhere from less than 500' above ground level (AGL) to several thousand feet AGL. If you do not have the
runway in sight at Minimums (measured using horizontal distance and or height AGL) , you need to hold until conditions improve or head for your alternate. Decision
Height (DH) is the altitude in AGL where you are committed to land although circumstances may still require balked landing procedures. Minimums can be found on
airport approach plates like Jeppsen's and DH should be programmed into your radar altimeter.
So, no definitive idea why this is happening but controlling your energy state to nail the necessary Vat or Vref is always a good plan and virtual pilot skill.
-C
Re: strange flight controls <100ft - adrian8891 - 20-06-2015
Thank You for answer.
Problem is that it occurs everytime. I use REX for weather and FSUIPC (or similar name...) for any addon.
It never pulled me up. It was always down.
Re: strange flight controls <100ft - Joeflyer - 20-06-2015
At that altitude, speed is being reduced by the default autopilot and possibly not trimming the aircraft accordingly. Once you disengage the AP at
such low altitude, the nose will drop for sure. I think default aircraft are quite bad on flight dynamics anyway. At any rate, try disengaging the AP
at 500 ft. AGL and see if it will be better for you to control the rate of descent with pitch and power.
Re: strange flight controls <100ft - adrian8891 - 20-06-2015
AGL? Can You explain?
Im going on approach with around 160kts. Sometimes I hold autothrottle till touchdown and sometimes I disengange it around
5nm from airport.
Re: strange flight controls <100ft - Leftcoaster - 20-06-2015
AGL = Above Ground Level (height as opposed to altitude which is ASL = Above Sea Level)
Approaching at 160 KIAS seems awfully fast for an A320, which would explain the trim problems. You're probably around 30+ KIAS or so above Vref when you reach the
threshold and so are forcing the aircraft to land when it still "wants" to fly.
Slow down and see what happens.
-C
Re: strange flight controls <100ft - adrian8891 - 20-06-2015
Strange, i use ATC Pro X, and before landing atc it advising me to reduce speed to 160kts. But after Your post, i tried to look
for speed ref for Airbus a321. And http://www.freechecklists.net/simchecklists.asp here I found checklist for this plane. There is
finał glidescope speed 145kts. Maybe this seems to be problem.
BTW, i never look after Trim setting. Is it important in any way?
Re: strange flight controls <100ft - Joeflyer - 20-06-2015
Yep, 160 knots is more in line with the approach speed of an MD-11.
Adrian, it's vitally important to adjust the trim on any airplane during every phase of flight....if you are hand flying it of course. Elevator trim
in particular helps to keep too much fore and aft pressure on the yoke and provides more stability/control during flight. It keeps a pilot from having
to work so hard
Possibly you should review more topics on what elevator, rudder and aileron trim do for an aircraft.Re: strange flight controls <100ft - Prosdocimo - 21-06-2015
Maybe this could be the solution. I know that below 100ft, A321 switches automatically his fly-by-wire system, from Airbus-like to Boeing-like direct inputs.
You could make the test approaching with the three buttons of Flight computer OFF (the three ones on overhead, namely ELAC1 SEC1 FAC1)
Re: strange flight controls <100ft - Joeflyer - 21-06-2015
Quote:Prosdocimo wrote:
Maybe this could be the solution. I know that below 100ft, A321 switches automatically his fly-by-wire system, from Airbus-like to Boeing-like direct
inputs.
You could make the test approaching with the three buttons of Flight computer OFF (the three ones on overhead, namely ELAC1 SEC1 FAC1)
Does the default A321 have this functionality??
Re: strange flight controls <100ft - Prosdocimo - 21-06-2015
Yes! I tried right now with default A321. Below 100ft AGL it changes to direct stick input
Re: strange flight controls <100ft - Joeflyer - 21-06-2015
Nice, didn't know the default a/c had such functionality
Re: strange flight controls <100ft - adrian8891 - 21-06-2015
Quote:Prosdocimo wrote:
You could make the test approaching with the three buttons of Flight computer OFF (the three ones on overhead, namely
ELAC1 SEC1 FAC1)
So, will this be sufficient?
Re: strange flight controls <100ft - Prosdocimo - 21-06-2015
Disabling those three switches you transfom A321's computer-controlled stick into direct-tradictional stick, so yes! Keep in mind that you will have to trim the aircraft as every no fly-by-wire airplane
Re: strange flight controls <100ft - aberleb91 - 22-06-2015
Next time check to see if spoilers are armed. They are not supposed to come up until you actually hit the ground but maybe there is a glitch?