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asuflyer
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Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 4:23 pm

A Batik Air A320 registration PK-LUT operating flight 6803 Jambi, Indonesia to Jakarta had to return to the departing airport due to the inability to retract the nosegear. Upon landing it was discovered the nosegear had rotated 90 degrees, which is a known issue with A320 series nosegears. A similar incident occurred with a Pegasus A320NEO in Basel earlier in the year.

Photos of the disabled aircraft

Image

Image

https://www.cnbcindonesia.com/news/2021 ... rn-to-base
 
GSPSPOT
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 5:10 pm

Also happened with a B6 flight to LAX quite some years ago.
Great Lakes, great life.
 
jetmatt777
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 5:16 pm

I believe that is the designed failsafe position of that particular nosegear. If it were to fail in any other direction (for example 40 degrees deflection), it could cause a high speed veer off of the runway. At 90 degrees the tire just melts.
 
Antarius
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 5:19 pm

jetmatt777 wrote:
I believe that is the designed failsafe position of that particular nosegear. If it were to fail in any other direction (for example 40 degrees deflection), it could cause a high speed veer off of the runway. At 90 degrees the tire just melts.


Ah makes sense.

Still, interesting. Didn't know this was an issue that's happened a few times before. What causes it?
Militant Centrist
Let's all just use some common sense
 
hayzel777
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 5:26 pm

Antarius wrote:
jetmatt777 wrote:
I believe that is the designed failsafe position of that particular nosegear. If it were to fail in any other direction (for example 40 degrees deflection), it could cause a high speed veer off of the runway. At 90 degrees the tire just melts.


Ah makes sense.

Still, interesting. Didn't know this was an issue that's happened a few times before. What causes it?

It's a well known issue with the centering cam of the nose wheel assembly. The 90-degree position is the plane's failsafe solution when it identifies a fault.
 
Max Q
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 5:33 pm

Makes no sense at all, amazing this known failure mode hasn’t been corrected
The best contribution to safety is a competent Pilot.


GGg
 
C525C
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 5:52 pm

Still holds the centerline better than I do.
 
cedarjet
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 6:03 pm

Happened to a Brazilian A330 operator landing at JFK as well, although weirdly, after a lot of preparation for an emergency and possible crash, it straightened out a few seconds before touchdown!
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
 
jetmatt777
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 6:45 pm

Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


Not really. There is a firm mechanical limit at 90 degrees, it is better to fail-default to a known position than any number of random positions that could cause a catastrophic loss of life. This happens every couple of years, out of hundreds of thousands (millions?) of A320 cycles around the world. Seems to be a pretty uncommon situation, and it fails in the safest known position.
 
Antarius
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 7:01 pm

jetmatt777 wrote:
Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


Not really. There is a firm mechanical limit at 90 degrees, it is better to fail-default to a known position than any number of random positions that could cause a catastrophic loss of life. This happens every couple of years, out of hundreds of thousands (millions?) of A320 cycles around the world. Seems to be a pretty uncommon situation, and it fails in the safest known position.


It makes sense that if it has to fail, for it to be in a consistent position and one that limits runway excursion.

That said, it doesn't make sense that this is a known issue. Surprised it hasn't gotten more emphasis to be fixed.
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YYZSpotter1991
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sat Mar 06, 2021 7:43 pm

GSPSPOT wrote:
Also happened with a B6 flight to LAX quite some years ago.


Instantly what I thought of when I saw the thread's title.
Toronto-based flyer since 1997
 
zuckie13
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 1:02 am

jetmatt777 wrote:
Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


Not really. There is a firm mechanical limit at 90 degrees, it is better to fail-default to a known position than any number of random positions that could cause a catastrophic loss of life. This happens every couple of years, out of hundreds of thousands (millions?) of A320 cycles around the world. Seems to be a pretty uncommon situation, and it fails in the safest known position.


Yeah, going to 90 degrees seems to be the best option if it can't guarantee control. My question is whether the underlying issue that seems to happen on these flights that leads to it needing to go to this mode should be investigated/fixed. It's still not ideal to be dragging the tire down the runway - certainly at least some increased risk, so if whatever part is failing that leads to this can be fixed, it wouldn't be a bad thing.
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 1:28 am

This seems to be happening quite often. Landing gear aren’t cheap to repair and overhaul. Why does this keep happening? Airbus tried to fix it years ago when it was attributed to the Brake and Steering Control Unit

AD NUMBER: 2005-24-06
MANUFACTURER: Airbus
SUBJECT: Airworthiness Directive 2005-24-06
SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all Airbus Model A318-100, A319-100,A320-200, A321-100, and A321-200 series airplanes, and Model A320-111 airplanes. This AD requires an inspection to determine whether certain braking and steering control units (BSCUs) are installed or have ever been installed. For airplanes on which certain BSCUs are installed or have ever been installed, this AD requires an inspection of the nose landing gear (NLG) upper support and corrective action if necessary, and a check of the NLG strut inflation pressure and an adjustment if necessary. For some of these airplanes, this AD also requires a revision to the aircraft flight manual to incorporate an operating procedure to recover normal steering in the event of a steering failure. This AD results from a report of an incident where an airplane landed with the NLG turned 90 degrees from centerline. We are issuing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


http://www.aero-news.net/index.cfm?do=m ... 4491c32428

It happened on an A320neo two months ago, so whatever is causing the gear to fail and go into this 90 degree safe mode still isn’t fixed

https://simpleflying.com/pegasus-a320ne ... wrong-way/

More events

https://www.aeroinside.com/12959/asiana ... on-landing

https://www.flightglobal.com/northwest- ... 86.article
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 1:35 am

Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


Airbus has tried and there is an Airworthiness Directive published, yet it still keeps happening.
 
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PA727
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 3:32 am

I don't understand the reasoning behind the default failure position being 45 degrees rather than straight ahead. Is there a mechanical or design reason for this default rather than just locking straight ahead? Genuinely interested in the "why?"
 
flyboy7974
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 3:37 am

YYZSpotter1991 wrote:
GSPSPOT wrote:
Also happened with a B6 flight to LAX quite some years ago.


Instantly what I thought of when I saw the thread's title.


Actually, was a B6 flight departing BUR for JFK, couldn't retract the gear, so circled the LA basin for hours to burn fuel.
 
InfinitePilot35
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 3:51 am

I agree, the 90 degree deflection is the best contingency plan in the worst-case scenario. Not extending the nose gear may cause damage to the fuselage and systems, a 45 degree deflection will cause a high speed runway excursion, while a 90 degree will only damage the tyre itself, not causing a serious accident.
 
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leleko747
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 3:56 am

cedarjet wrote:
Brazilian A330 operator


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I wonder when people will understand:
Embraer 190 or simply E190, not ERJ-190. E-Jets are NOT ERJs!
Boeing 747-8, not Boeing 747-800. Same goes for 787.
Airbus A320, not Airbus 320.
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MavyWavyATR
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 4:04 am

I thought Airbus fixed that issue already after B6 292.
 
TheF15Ace
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 4:09 am

For anyone interested on what the landing would've looked like, here's the video from the JetBlue incident at LAX

https://www.youtube.com/watch?v=RgnkY4x ... amroaligat
 
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DarkSnowyNight
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 4:13 am

It is actually 90 degrees. I fails this way in the event that the wheel cannot be centered. Things like loss of HYD pressure can cause this, and make the NLG unable to center. At that point, the Wheel is pushed back into the safe position. As mentioned above, the why is centered around the idea of it being better to have a fail occur in a known position. Even better so still that the known position will not take the aircraft off the RWY.

jetmatt777 wrote:
Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


Not really. There is a firm mechanical limit at 90 degrees, it is better to fail-default to a known position than any number of random positions that could cause a catastrophic loss of life. This happens every couple of years, out of hundreds of thousands (millions?) of A320 cycles around the world. Seems to be a pretty uncommon situation, and it fails in the safest known position.


Absolutely. Aviation design is actually full of design Fail Safes like that.

And this is an uncommon failure. But there have been a few recently. Based on the ADs, I would guess that it is more of statistical anomaly for this year rather than a real trend.
Well, you know what they say. Whatever doesn't kill you...
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FlyingElvii
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 5:28 am

C525C wrote:
Still holds the centerline better than I do.

“ More right rudder, dammit!” - Every CFI everywhere....
 
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zeke
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 6:08 am

Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


There is no single failure mode that results in this. What is evident is the safe position that is goes to has resulted in 100% safe outcomes.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
bennett123
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 11:08 am

If it can default to 90 degrees, why not default to 0 degrees?.
 
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FabDiva
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 11:15 am

bennett123 wrote:
If it can default to 90 degrees, why not default to 0 degrees?.


it's better to spring load it up against the stops one way or the other then try and line it up in the middle when you can't be sure it's centred.
 
bennett123
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 11:52 am

Right.

My thinking seemed so obvious. I suspected that if it was an option that someone else would thought of it first.
 
cskok8
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 1:53 pm

Good landing
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 2:05 pm

zeke wrote:
Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


There is no single failure mode that results in this. What is evident is the safe position that is goes to has resulted in 100% safe outcomes.


Airbus has attempted to fix the condition, but has been unsuccessful. Despite safe outcomes so far, the FAA and EASA have determined that the nose gear at 90 degrees reduces controllability and is an unsafe condition

From Airworthiness Directive 2005-24-06
Unsafe Condition

(d) This AD results from a report of an incident where an airplane landed with the nose landing gear (NLG) turned 90 degrees from centerline, and from additional reports of NLG upper support anti-rotation lugs rupturing in service. We are issuing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


https://www.federalregister.gov/documen ... -airplanes
 
Interflug74
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 2:24 pm

Don´t happend on properly maintained planes? Like MCAS 1.0 isn´t a problem with well trained western pilots?
 
dr1980
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 2:27 pm

TheF15Ace wrote:
For anyone interested on what the landing would've looked like, here's the video from the JetBlue incident at LAX

https://www.youtube.com/watch?v=RgnkY4x ... amroaligat


Thanks for this. It looks like they did not deploy the thrust reversers? I’m assuming that’s part of the emergency procedure for a situation like this but I’m curious why, I would think they’d want to slow down as quick as possible once on the runway?
Dave/CYHZ
 
CRJ200flyer
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 2:52 pm

dr1980 wrote:
TheF15Ace wrote:
For anyone interested on what the landing would've looked like, here's the video from the JetBlue incident at LAX

https://www.youtube.com/watch?v=RgnkY4x ... amroaligat


Thanks for this. It looks like they did not deploy the thrust reversers? I’m assuming that’s part of the emergency procedure for a situation like this but I’m curious why, I would think they’d want to slow down as quick as possible once on the runway?


I’m a CRJ-200 pilot, so take this idea knowing that. On my airplane it’s not uncommon for the thrust reversers to deploy and spool up unevenly, causing aircraft yaw. In some cases it’s taken a great deal of control input to counter this yaw. With a long runway, perhaps applying reverse thrust wasn’t deemed worth the risk with in an inoperable nose wheel? As the aircraft decelerates, the rudder is ever less effective, so the only thing to correct this yaw moment would be the nose wheel, which of course is not functioning in this emergency.

Another idea is perhaps reverse thrust on an A320 applied while holding the nose wheel up can cause the nose to come down more rapidly if sufficient back pressure isn’t applied, causing increased pressure on the nose landing gear. I don’t know, just brainstorming here!
 
B6JFKH81
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 4:21 pm

When B6 292 happened, we performed a Messier service bulletin for a certain number of aircraft to change out a limiting ring in the NLG strut, which had a weak point in the stop tabs. Aircraft delivered beyond a certain time already had this new ring so it was only our older aircraft. That was all the way back in 2005/2006. All aircraft in the fleet at that time were under 10 years of age so didn't have gear changes yet.

PK-LUT is a 2017 delivery so the NLG would already have this SB incorporated, I am quite interested to see what caused this rotation as the new ring seemed to fix the issue and that was 15 years ago now! God I'm getting old LOL!
"If you do not learn from history, you are doomed to repeat it"
 
WayexTDI
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 6:37 pm

PA727 wrote:
I don't understand the reasoning behind the default failure position being 45 degrees rather than straight ahead. Is there a mechanical or design reason for this default rather than just locking straight ahead? Genuinely interested in the "why?"

Default failing position is 90°, not 45. 90° is the mechanical limit, so they can let the steering run until it hits that point.
0° position (straight ahead) is the middle of the actual operating range (it'd be ± X°) and cannot be set at that position unless the actual position is known; i.e. it cannot be used as "fail safe".
 
WayexTDI
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 6:40 pm

Weatherwatcher1 wrote:
zeke wrote:
Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


There is no single failure mode that results in this. What is evident is the safe position that is goes to has resulted in 100% safe outcomes.


Airbus has attempted to fix the condition, but has been unsuccessful. Despite safe outcomes so far, the FAA and EASA have determined that the nose gear at 90 degrees reduces controllability and is an unsafe condition

From Airworthiness Directive 2005-24-06
Unsafe Condition

(d) This AD results from a report of an incident where an airplane landed with the nose landing gear (NLG) turned 90 degrees from centerline, and from additional reports of NLG upper support anti-rotation lugs rupturing in service. We are issuing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


https://www.federalregister.gov/documen ... -airplanes

Of course it results in reduced controllability of the plane... since the nose gear is no longer commanded...
However, as was said many times upthread, that reduced controllability is still a better outcome than failure in a random position that would "control" the aircraft out of the runway...
 
ozark1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 7:04 pm

Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected

Yes it really is interesting that this keeps happening. I think the JetBlue incident brought it to everyone’s attention, but I have read of several other identical nose gear problems. The B6 happened at LAX, with advance notice to the media and plenty of drama. I wonder if the same problem had happened before this one, but was repaired prior to flight or occurred at a time and place that garnered less or no notice.
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 7:07 pm

WayexTDI wrote:
Weatherwatcher1 wrote:
zeke wrote:

There is no single failure mode that results in this. What is evident is the safe position that is goes to has resulted in 100% safe outcomes.


Airbus has attempted to fix the condition, but has been unsuccessful. Despite safe outcomes so far, the FAA and EASA have determined that the nose gear at 90 degrees reduces controllability and is an unsafe condition

From Airworthiness Directive 2005-24-06
Unsafe Condition

(d) This AD results from a report of an incident where an airplane landed with the nose landing gear (NLG) turned 90 degrees from centerline, and from additional reports of NLG upper support anti-rotation lugs rupturing in service. We are issuing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


https://www.federalregister.gov/documen ... -airplanes

Of course it results in reduced controllability of the plane... since the nose gear is no longer commanded...
However, as was said many times upthread, that reduced controllability is still a better outcome than failure in a random position that would "control" the aircraft out of the runway...


90 is better than 45, but the regulatory authorities have determined that it is still an unsafe condition. Why has this happened over a dozen times? Are any other airplanes losing nose gear steering and destroying the nose gear so often? I’m guessing that EASA and FAA have determined that the gear stuck at 90 degrees is unsafe since a contaminated runway with a crosswind could make the situation much worse.
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Sun Mar 07, 2021 7:11 pm

CRJ200flyer wrote:
dr1980 wrote:
TheF15Ace wrote:
For anyone interested on what the landing would've looked like, here's the video from the JetBlue incident at LAX

https://www.youtube.com/watch?v=RgnkY4x ... amroaligat


Thanks for this. It looks like they did not deploy the thrust reversers? I’m assuming that’s part of the emergency procedure for a situation like this but I’m curious why, I would think they’d want to slow down as quick as possible once on the runway?


I’m a CRJ-200 pilot, so take this idea knowing that. On my airplane it’s not uncommon for the thrust reversers to deploy and spool up unevenly, causing aircraft yaw. In some cases it’s taken a great deal of control input to counter this yaw. With a long runway, perhaps applying reverse thrust wasn’t deemed worth the risk with in an inoperable nose wheel? As the aircraft decelerates, the rudder is ever less effective, so the only thing to correct this yaw moment would be the nose wheel, which of course is not functioning in this emergency.

Another idea is perhaps reverse thrust on an A320 applied while holding the nose wheel up can cause the nose to come down more rapidly if sufficient back pressure isn’t applied, causing increased pressure on the nose landing gear. I don’t know, just brainstorming here!


I would assume that The airplane also has differential braking available once rudder effectiveness is reduced as the plane slows down. In dry conditions without a crosswind, that should help keep the airplane straight.

On a plane with wing mounted engines, doesn’t reverse thrust compress the nose gear strut further when the plane slows down? That would be bad if the airplane is grinding on the axle.
 
prebennorholm
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 1:53 am

bennett123 wrote:
If it can default to 90 degrees, why not default to 0 degrees?.

Landing in sidewind and the nosegear stuck at 0 degrees would often result in high speed runway departure.

To default at 90 degrees when nosegear steering fails is the safest option.

(Problem is that nosegear steering shall not fail)
Always keep your number of landings equal to your number of take-offs
 
FluidFlow
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 9:09 am

Having the nose gear stuck at + or - 90° (which one is it actually?) is really safe as it has the exact same properties as if you would lock the breaks up at exactly 0°. You retain a lot of control that way.
If you ever drove a non ABS supported car, it is important that the front wheels lock before the back wheels to retain control. That way you keep course straight.

Now if you have wind, the rudder gives you the authority to stay on course because it has way more influence than the actual nose wheel due to the sheer size and its position. Together with the kinetic energy of an aircraft, the tendency to go straight ahead is really large.

That is why you see aircraft missing the exit and skidding of the runway when they are too fast because the aircraft tends to go straight instead of turning.

What would be really dangerous is having the nose gear locked at 90° and one side of the MLG blowing a tyre or locking the breaks. That would almost instantly lead to a sharp turn, because the nose gear would not counteract the turning moment caused by the one sided breaking of the MLG.
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 1:17 pm

FluidFlow wrote:
Having the nose gear stuck at + or - 90° (which one is it actually?) is really safe as it has the exact same properties as if you would lock the breaks up at exactly 0°. You retain a lot of control that way.
If you ever drove a non ABS supported car, it is important that the front wheels lock before the back wheels to retain control. That way you keep course straight.

Now if you have wind, the rudder gives you the authority to stay on course because it has way more influence than the actual nose wheel due to the sheer size and its position. Together with the kinetic energy of an aircraft, the tendency to go straight ahead is really large.

That is why you see aircraft missing the exit and skidding of the runway when they are too fast because the aircraft tends to go straight instead of turning.

What would be really dangerous is having the nose gear locked at 90° and one side of the MLG blowing a tyre or locking the breaks. That would almost instantly lead to a sharp turn, because the nose gear would not counteract the turning moment caused by the one sided breaking of the MLG.


A contaminated runway causing uneven braking or significant crosswind would be much more difficult to control. That may be why the regulators have determined that the nose gear stuck at a 90 degree angle is an unsafe condition.

Weatherwatcher1 wrote:
zeke wrote:
Max Q wrote:
Makes no sense at all, amazing this known failure mode hasn’t been corrected


There is no single failure mode that results in this. What is evident is the safe position that is goes to has resulted in 100% safe outcomes.


Airbus has attempted to fix the condition, but has been unsuccessful. Despite safe outcomes so far, the FAA and EASA have determined that the nose gear at 90 degrees reduces controllability and is an unsafe condition

From Airworthiness Directive 2005-24-06
Unsafe Condition

(d) This AD results from a report of an incident where an airplane landed with the nose landing gear (NLG) turned 90 degrees from centerline, and from additional reports of NLG upper support anti-rotation lugs rupturing in service. We are issuing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


https://www.federalregister.gov/documen ... -airplanes
 
FluidFlow
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 1:59 pm

Weatherwatcher1 wrote:
FluidFlow wrote:
Having the nose gear stuck at + or - 90° (which one is it actually?) is really safe as it has the exact same properties as if you would lock the breaks up at exactly 0°. You retain a lot of control that way.
If you ever drove a non ABS supported car, it is important that the front wheels lock before the back wheels to retain control. That way you keep course straight.

Now if you have wind, the rudder gives you the authority to stay on course because it has way more influence than the actual nose wheel due to the sheer size and its position. Together with the kinetic energy of an aircraft, the tendency to go straight ahead is really large.

That is why you see aircraft missing the exit and skidding of the runway when they are too fast because the aircraft tends to go straight instead of turning.

What would be really dangerous is having the nose gear locked at 90° and one side of the MLG blowing a tyre or locking the breaks. That would almost instantly lead to a sharp turn, because the nose gear would not counteract the turning moment caused by the one sided breaking of the MLG.


A contaminated runway causing uneven braking or significant crosswind would be much more difficult to control. That may be why the regulators have determined that the nose gear stuck at a 90 degree angle is an unsafe condition.

Weatherwatcher1 wrote:
zeke wrote:

There is no single failure mode that results in this. What is evident is the safe position that is goes to has resulted in 100% safe outcomes.


Airbus has attempted to fix the condition, but has been unsuccessful. Despite safe outcomes so far, the FAA and EASA have determined that the nose gear at 90 degrees reduces controllability and is an unsafe condition

From Airworthiness Directive 2005-24-06
Unsafe Condition

(d) This AD results from a report of an incident where an airplane landed with the nose landing gear (NLG) turned 90 degrees from centerline, and from additional reports of NLG upper support anti-rotation lugs rupturing in service. We are issuing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


https://www.federalregister.gov/documen ... -airplanes



The regulator said this:

We are proposing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


The bold font is from me. The FAA did not said is an unsafe condition but it could turn into one.

That is also the reason (I believe) that this AD does not mandate Airbus to change the design, but to mandate repetitive inspections to make sure the NLG does work accordingly:

This proposed AD would require repetitive inspections of the NLG upper support, and related investigative/corrective actions in accordance with new service information; and would remove the one-time inspection that was required by the existing AD


So if the NLG is locked we can assume there was a failure of the upper support of the NLG that was either missed in the inspection or did occur more frequent than expected.

It is a bit like inflight engine shut downs. They can result in unsafe conditions and there are multiple ADs etc. that make sure they happen as infrequent as possible. They still do happen and almost always do not end in an accident.
Same with the 90° nose wheel lock. It should not happen but it does and when it does it still is almost always no problem (as history shows). Still it should not happen hence the AD to make inspections.
But the "danger" is so small no permanent fix is needed.
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 2:13 pm

FluidFlow wrote:
FluidFlow wrote:


Weatherwatcher1 wrote:

Airbus has attempted to fix the condition, but has been unsuccessful. Despite safe outcomes so far, the FAA and EASA have determined that the nose gear at 90 degrees reduces controllability and is an unsafe condition

From Airworthiness Directive 2005-24-06


https://www.federalregister.gov/documen ... -airplanes



The regulator said this:

We are proposing this AD to prevent landings with the NLG turned 90 degrees from centerline, which could result in reduced controllability of the airplane.


The bold font is from me. The FAA did not said is an unsafe condition but it could turn into one.

That is also the reason (I believe) that this AD does not mandate Airbus to change the design, but to mandate repetitive inspections to make sure the NLG does work accordingly.


For reference, NPRMs are always written in a tense saying that the condition COULD exist. Whatever failure that can cause the unsafe condition is not assumed to be on all airplanes. It doesn’t change the fact that the FAA has determined that the loss of steering control from a 90 degree nose gear reduces controllability, which is the unsafe condition that the FAA issued the AD to prevent in the past.


FluidFlow wrote:
But the "danger" is so small no permanent fix is needed.


That depends on the functional hazard assessment which feeds the failure modes and effects analysis. Is loss of steering hazardous or major? Depending on the FHA, the probability will need to be less than 1 in 10million (hazardous) or less than 1 in 100,000 (major). If it is hazardous (which may explain the prior AD), then Airbus will need to do a statistical analysis based on the number of events that have occurred to determine if the airplane meets the regulations in FAR 25.1309

https://www.faa.gov/regulations_policie ... ntID/22680
Last edited by Weatherwatcher1 on Mon Mar 08, 2021 2:25 pm, edited 1 time in total.
 
User avatar
zeke
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 2:25 pm

FluidFlow wrote:
The bold font is from me. The FAA did not said is an unsafe condition but it could turn into one

That is also the reason (I believe) that this AD does not mandate Airbus to change the design, but to mandate repetitive inspections to make sure the NLG does work accordingly:


The AD linked is around 15 years old and is not be relevant to todays aircraft, the BSCU versions mentioned are pretty old and not considered complaint in todays world, around 7 years ago a new BSCU version was mandated by a different AD. In my view this is simply a case of someone doing a google search and posting the first link they could find without actually understanding the issue.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 2:27 pm

zeke wrote:
FluidFlow wrote:
The bold font is from me. The FAA did not said is an unsafe condition but it could turn into one

That is also the reason (I believe) that this AD does not mandate Airbus to change the design, but to mandate repetitive inspections to make sure the NLG does work accordingly:


The AD linked is around 15 years old and is not be relevant to todays aircraft, the BSCU versions mentioned are pretty old and not considered complaint in todays world, around 7 years ago a new BSCU version was mandated by a different AD. In my view this is simply a case of someone doing a google search and posting the first link they could find without actually understanding the issue.


I find your comment rather insensitive assuming that I am not familiar with landing gear, steering, maintenance, Airworthiness Directives or FAR 25.1309 for the certification bases of airplanes. Clearly there is an AD meant to address the condition of a nose gear at 90 degrees. The AD is meant to address the condition from years past and the failure effect of loss of steering is still relevant.
 
CMHChris
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 2:39 pm

On February 16, 1999, at 1602 Eastern Standard Time, an Airbus A-320-231, N628AW, operated by America West Airlines as flight 2811, received minor damage when it landed at Port Columbus International Airport (CMH), Columbus, Ohio, with the nose wheels rotated 90 degrees. There were no injuries to the 2 certificated pilots, 3 flight attendants and 26 passengers. https://www.jamesdecamp.com/1999/02/16/ ... ight-2811/
 
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zeke
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 2:50 pm

Weatherwatcher1 wrote:
I find your comment rather insensitive assuming that I am not familiar with landing gear, steering, maintenance, Airworthiness Directives or FAR 25.1309 for the certification bases of airplanes. Clearly there is an AD meant to address the condition of a nose gear at 90 degrees. The AD is meant to address the condition from years past and the failure effect of loss of steering is still relevant.


A person who is knowledgeable in this field would have known that NPRm posted was superseded 7 years ago.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
meecrob
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Mon Mar 08, 2021 10:52 pm

'The unsafe condition is the NLG turning 90 degrees from centerline, which could result in reduced controllability of the airplane. You may obtain further information by examining the MCAI in the AD docket."

I think it helps to read these as if they were written in legalese. An "unsafe condition" usually refers to any configuration of the plane that is not in accordance with the maintenance manuals. It doesn't mean that an accident/incident is imminent, it means the aircraft will behave differently than if the failure had not occurred. Logically, we all know that if a nosewheel fails in such a way that it destroys itself, but keeps the plane on the runway, that it is a more optimal failure condition than one that induces the aircraft to leave the runway, but is "unsafe" compared to a nosewheel that did not fail in the first place.
 
Weatherwatcher1
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Tue Mar 09, 2021 2:48 am

meecrob wrote:
'The unsafe condition is the NLG turning 90 degrees from centerline, which could result in reduced controllability of the airplane. You may obtain further information by examining the MCAI in the AD docket."

I think it helps to read these as if they were written in legalese. An "unsafe condition" usually refers to any configuration of the plane that is not in accordance with the maintenance manuals. It doesn't mean that an accident/incident is imminent, it means the aircraft will behave differently than if the failure had not occurred. Logically, we all know that if a nosewheel fails in such a way that it destroys itself, but keeps the plane on the runway, that it is a more optimal failure condition than one that induces the aircraft to leave the runway, but is "unsafe" compared to a nosewheel that did not fail in the first place.


Here is some useful information on what an unsafe condition is and how it results in Airworthiness Directives

7.10.4 Airworthiness Directives
Airworthiness Directives (ADs) are issued by the FAA when an unsafe condition exists in a type-certificated product, and that condition is likely to exist in other products of the same type design. ADs have the same authority as FARs, and as such, compliance with an Airworthiness Directive is mandatory. Noncompliance with an AD would be in violation of the terms of issuance of the Airworthiness Certificate, resulting in its invalidation—in effect, grounding the aircraft. The same effect would result if an engine, propeller, or appliance with an unincorporated AD is installed on an aircraft.


And a little more information:

The need for an AD may be brought to light as a result of an accident, maintenance problems, routine inspections, etc., the primary criteria being that an unsafe condition was found that is likely to exist in other aircraft.


https://www.sciencedirect.com/topics/en ... -directive


Since the FAA has previously determined the following

The unsafe condition is the NLG turning 90 degrees from centerline, which could result in reduced controllability of the airplane


https://www.federalregister.gov/documen ... -airplanes

It is possible we may see another Airworthiness Directive to come since we’ve seen multiple A320s land with the nose gear at 90 degrees in the last year including an A320neo, unless of course the FAA and EASA have determined that it is no longer an unsafe condition
 
Chemist
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Tue Mar 09, 2021 5:06 am

If the NG turned 90 degrees is to prevent runway excursions and is a safety mechanism, how is it that the A32x series seems to be the only commercial A/C with this behavior? How do all the others (737/747/757/767/777/787/A300/A330/A340/A350/A380/plus many others from not the Big Two) handle the same issue without the same result?
 
meecrob
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Re: Batik Air A320 lands with nosegear turned 90 degrees

Tue Mar 09, 2021 4:50 pm

Weatherwatcher1 wrote:


None of what you copied and pasted says anything different from what I said. My point is that "unsafe" to the FAA means something different than what you would find in the dictionary, similar to the word "theory" in scientific vs non-scientific discussion.

"Unsafe" to the FAA means it does not conform to its TCDS. Clearly an aircraft does not conform to its TCDS if its nosegear is locked 90* to one side. Also clearly, you cannot use the same instructions from the manual with regards to nosewheel steering/tiller operation, etc. The FAA is covering its ass by using the term "unsafe" because they said "the operation of XXXX aircraft is safe if you follow our approved manual, and the aircraft conforms to the TCDS". The corollary is that if anything does not conform, then they could be held liable if an incident/accident occurred, so they use a blanket statement that in essence says "if absolutely anything on this aircraft is outside of these limits, the aircraft is 'unsafe' because we didn't test it in this configuration", not "unsafe because it will cause an accident/incident"

There is a huge difference between "we don't have all the info, so just don't do it" and "if you do this, something bad will happen"


Chemist wrote:


I'm guessing here, but I think that the A32X design was more of a design flaw that they put a cherry on top of than an actual design goal. "We can't reliably get it to stop failing (in a certain timeframe, under a certain budget, under a certain weight, etc.), so lets make it fail in a known way"

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