Is a Nose Gear Lock Pin necessary on pushback?

[maxalt]

Bit of a debate here about the necessity of a NLG lock-pin for pushbacks.

Does your company use them - and if not, why not?

[411A]

L10, not required, nor necessarily desired.
One more thing for the ground crew to forget...:ugh:

[HAWK21M]

If L/G System is Pressurised Hydraulically.The Disconnect Pin Isolates the Pressure & return lines to the Steering Actuators & helps create a runaround between the Actuators to enable the NLG to move freely with the Tow Bar.
Engines can be started on Pushback saving Vital time.
The Steering pin with Red streamer is removed after the Tow bar is disconnected & shown to the Pilot at Taxi clearence by Ground crew.

regds
MEL

[belowMDA]

Hawk21m I think you are talking about the nose gear steering bypass pin as opposed to normal gear lock pins in general.

We do not use lock pins for push back nor do I see the need for them. The gear would have been designed not to require the pin installed for pushback. Also the pins are stored in the flight deck so lgistical issues about returning them remain, unless the tug has a whole bunch of spares.

[HAWK21M]

You are correct.I was referring to the Steering Disconnect pin.
Te LG lock pins are not used during Pushback during Normal ops,However We do use them during Mx Pushback/Towing ops.
regds
MEL

[Itswindyout]

this is also discussed by us, on a regular basis.

it is suggested that on push back and on a tow, from stand to deice, 9for example), ALL three pins should be in.

So my question is: on a Gulfstream 5/550, is it required to have the main gear pins in, for either function, and/or is it necessary for the nose pin to be in.

Assuming that the hydraulic pressures are being suppoerted.

windy

[maxalt]

Its the LOCK PIN I'm referring to here - not the steering disconnect pin.

OK, I'll rephrase the question.
On my Airbus the nose gear LOCK pin acts to prevent undesired movement of the the over-centre lock actuator mechanism.
The over-centre mechanism keeps the gear mechanically locked down. If this over-centre mechanism were to fail during (for example) emergency braking by the tug on pushback - would it result in a gear collapse?

Some say NO - you would have to operate the gear handle to (hydraulically) operate the actuator which breaks the down lock before you could get a retraction, and nobody is likely to do THAT. Hence you don't need a pin.

Others say YES - if you had a hydraulic failure to the actuator coupled with a sudden stop by the tug, it would be possible for the over-centre to break and allow gear collapse.

Having a pin in may be belt and braces - depending on your point of view above - but the only drawback I can see in having it in is that (as 411A said) somebody might forget to remove it some day.

FWIW, we use them, and nobody has had one left in after push-back for at least the last 20 years.

[Jet II]

FWIW, we use them, and nobody has had one left in after push-back for at least the last 20 years.

Who do you work for - in over 20 years in the industry I have never known any major airline insist on fitting ground lock pins for pushback.

In fact the ground-pins are kept on the aircraft and there has been a continued effort to stop people using 'spare' ground pins that cannot be controlled as they tend to get left in - turnbacks due to pins left in and gear retraction failure are not unkown.

[mono]

Err Max, I thought you flew for us? We don't use a nose gear lock pin for pushback! certainly not here at LGW.:=

The whole point of the mechanism is that it is over-centre. In order to break, it has to go through the centre, inline position so that it can pivot in the normal way and therefore allow the gear to retract. Any pressure on it will tend to increase the over-centre pushing against the lock stops in the opposite direction to that which is required to retract the gear.

I have had to manually break the lock to retract the gear in order to allow a nose leg seal change. It takes a 5 foot bar and a good heft to get the lock back through overcentre to allow the gear to retract with no hydraulics applied and I'm 6'3" and 100 Kgs. :eek:

[Swedish Steve]

Who do you work for - in over 20 years in the industry I have never known any major airline insist on fitting ground lock pins for pushback.
.
There was a time from about 1979-86 ish when it was a required procedure on the Tristar. There was a failure mode of the undercarriage selector mechanism which retracted the gear with hyds on and an AC power failure. In all that time we used NLG lock pins for push back. We had special ones made with long metal sticks on them so they could be easily removed after pushback. Since then I have never used them on pushback. The hydraulics are pressurised and the pin is redundant. It would need the failure of two big springs, and the hydraulics, and the tug to give a push.
When towing aircraft unpowered, we use a NLG pin only. Some airlines here use all the gear pins, but our airline does not require it, and I agree with this. NLG usually retracts forwards, which means the tyres roll across the tarmac. MLG retracts sideways so the tyres have to scrub across the tarmac.

[maxalt]

Err Max, I thought you flew for us? Whaddya mean 'us' Keemosabi?

As I suspected though - seems very few are using the NLG lock pin nowadays.

Anybody from Emirates here? Whats YOUR company SOP on this?

[Denzil]

I believe BA pushed a TriStar (many years ago) minus the NLG downlock pin & had a coming together of the aircraft & the tug.

[boeingdream787]

Nope.Never used one of those in EK either.Neither in my previous company on NGs.It sure would be a bad day if your over centre locks were to fail AND your hydraulics were to fail AND you got yourself the worst tug driver in the shift,who THEN decides to do a sudden stop!!! Which is exactly why they have been rendered redundant.Besides ofcourse the logistics involved in keeping a "spare" set in the tug.Which is exactly how the problem started to begin with!
Also some airlines have a legal requirment for the Captain to positively see and identify the three pins 'fore commencing taxy.Cheers anyays.

[411A]

Swedish Steve is indeed correct about the TriStar, and this specific selector valve condition was corrected by manufacturer service bulletin quite a long time ago.

[Koan]

Any current EMB-145 drivers care to comment on the Steering Disconnect PB?

[matkat]

As a line Engineer I never once used a nose gear pin for push back simply it is very difficult to get out(B747s) and it is also easy to forget, anytime We had them in for maintenance a log book entry would always be made to this effect.Nose gear steering by pass pins were of course always fitted(or whatever was used to isolate/disconnect nose wheel stearing) and removed on finish of push back.

[Rusty443]

I would like to comment from the rampie side, boys and girls!

First there is three ways of depressurisation,

1: CB
2: PIN
3: DISCONNECT THE TORQUE LINK

As for gear locks this refers to a/c types such as MD83 or SAAB 340 /2000 Etc.

Remember safety is the importance and a/c differs with type?

Also different Airlines and aircraft specify different rules.

No HYD can cause a nose wheel to fail, these rules are written into ramp manuals for safety it will never happen?

SO WHY IS IT WRITTEN?

[Rusty443]

As a line Engineer I never once used a nose gear pin for push back simply it is very difficult to get out(B747s) and it is also easy to forget, anytime We had them in for maintenance a log book entry would always be made to this effect.Nose gear steering by pass pins were of course always fitted(or whatever was used to isolate/disconnect nose wheel stearing) and removed on finish of push back.


THERE IS ALWAYS A REASON WHY (SAFETY)

IF IT IS DIFFICULTTO PULL THERE IS NORMALLY A PROBLEM?

:= STIFF MEANS UNSAFE???????????????????

FORGETFULL MEANS COMPLACENCY????????????????????????

[matkat]

THERE IS ALWAYS A REASON WHY (SAFETY)
IF IT IS DIFFICULTTO PULL THERE IS NORMALLY A PROBLEM?
:= STIFF MEANS UNSAFE???????????????????
FORGETFULL MEANS COMPLACENCY????????????????????????
Rusty I guess You have never heard of Murphys law then? complacency is removed from the equation by means of the log book entry I never said it was stiff to remove I said difficult so again I presume You have never worked 747s
as I said I have never been required to fit a gear nose pin, must be a good reason why not! and if it was required why not go the whole hog and fit pins to all the gear whilst pushback wonder how many turn back would occur then?

[saurabh]

If steering bypass pin on steering actuator of nose landing gear is not installed on B737NG then sys A hyd. pumps(both) should be off and alternate steering not selected(sys B).:ugh:

[theoldbull]

Not all aircraft are the same. However most modern RPT a/c that I have worked on such as B737, B747, B767, B777, A320, A330, A340 require considerable hydraulic pressure (approx 1650 PSI) to the "gear up" hydraulic circuit to unlock the individual gear lock actuator(s) to break the over centre lock.
The only way to achieve this is to have the applicable system pressurised and to move the gear lever to "UP". Again the above a/c all have interlock systems that require the a/c weight to be off one or more of the gears before the lever can be moved to "UP".
Any force in either direction on the nose gear, or in fact the main gears only forces the over centre lock towards the lock position.
The B707 was one a/c that did not have a very positive overcentre lock and most airlines required the fitting of a "bicycle handle" type nose pin for pushbacks on this a/c.

[Rusty443]

:oh:

My apologies MATKAT I did misread your bits, blame it on the fumes!

As for NLG pins I have experience on a few occasions of NLG fitted to 747’s on pushback and they have forgotten to pull them and the aircraft have had to dump fuel before landing to have it removed. (Not me and Companies I have not worked for)

Reference: the fitting of NLG pins for push was that some aircraft depressurise their systems so the possibility of a pull forward etc could collapse the NLG. This possibly answers the question why not fit all?

So I think basically that it is some Companies requirements that they either do or don’t?

The normal requirement for towing is fit all and tech log it.

For push and towing most ground handling companies have their own pins so that is the ones that do not go in the tech log hence the incidents above.:*

[aguila320]

The pin must be only be inserted in case of PULL the plane. In this case is mandatory to insert the pin.
In case of PUSH the plane it's not needed, it depends on the plane to need or not the nose wheel steering by-pass.

This is the way how spanish airlines work.

Best regards

[Rusty443]

Any current EMB-145 drivers care to comment on the Steering Disconnect PB?

I do know for a fact that to airlines that fly the EMB 145 do diconnect the steering bypass circuit breaker on arrival as it is in thier checklist for shut down.

Ground crews are supposed to check with the flt deck that this is pulled before tow bar connection.

It is then re-connected after push and after towbar has been disconnect and ground equipment clear.:ok:

Again I still would like to stress that different airlines have different procedures for pushing and towing.

The most common aircraft that company's like both NLG & Depressure pins fitted are the SAAB 340 & 2000. :8

[TR4A]

I fly the B737 and we don't use the nose wheel steering pin. We turn off the "A" pumps. Company started with the B737-200 which does not have the lockout. Now flying -300, -500, and -700. The -200's are gone and still turn off pumps for push back.

[I-2021]

Hello,

very interesting topic, but I don't understand about what kind of pins we are talking about...:ugh:

[Rusty443]

I must say one must stop reading and replying when I come home from the pub!!:hmm:

Interesting that we all seem to get confused that the origional comment was on Nose Landing Gear Pins (NLG) and we all go straight on to Depressure Pins?

Most aircraft that I have pushed back always have the depressure pin / torque link disconnected or the CB pulled. This covers most types of aircraft.

As for NLG for push back only the SAAB's use both and are handed back to the flt deck via the hatch.

Towing, all pins are fitted from flt deck and TECH LOGGED.:8

[HZ123]

At BA mainline all pushbacks have the pin inserted as the tow crew will bring the required type. As part of the procedure the headset man will tell flight deck that he will clear to P 1 or P 2 side of the aircraft and hold up the pin and tape in his left hand to show it has been removed. Or to be more accurate this is what should happen? Watching pushbacks by various companies and at times including BA many of them are very slapdash and seem to have little or no procedures in place.

[Captain Rat]

HZ123 you are talking about the 'Steering depressurisation/bypass pin' the original question is about the Nose gear downlock pin...which prevents the gear from retracting.
Most airlines I have been involved with fit the downlock pin only for towing the aircraft, often they are towed without any hydraulic pwer on (towbarless tugs etc). For normal pushbacks then the downlock pin is not fitted. However it will depend on each companies own policy. I do know of one major airline at LHR that fits the downlock pins for push backs. just means that the ground crew will have to show 2 pins to the crew before they taxi off.

[HZ123]

CR Thanks I realise they are intirely different but the thread has muddyed. Is the nose gear locking device the same then as that long bar that is placed upward on the 747 forward nosegear?

[Perrin]

AFTER 42 YEARS AS A LAE I HAVE NEVER I REPEAT NEVER PUT IN A DOWNLOCK PIN FOR A PUSH BACK AND HAVE NEVER WORKED FOR A AIRLINE (6) THAT WANTED YOU DO. AS WAS STATED THE AIRCRAFT IS BUILD NOT TO NEED ONE AND ITS ANOTHER THING TO FORGET ON PUSHBACK ON A WINDY WET DAY OR NIGHT WHEN THINGS CAN GET A BIT BUSY. KEEP THEM OUT AND KEEP THEM FLYING. FROM PAPA PETE

[Rusty443]

[QUOTE=Perrin]AFTER 42 YEARS AS A LAE I HAVE NEVER I REPEAT NEVER PUT IN A DOWNLOCK PIN FOR A PUSH BACK AND HAVE NEVER WORKED FOR A AIRLINE (6) THAT WANTED YOU DO.

Why do two airlines (that I know for a fact) fit them on push back this is referring back to the NLG & De-pressure pin on SAAB 340 / 2000?

The procedure is to hand pins back to the Captain through a hatch after completion of pushback. (TO ELIMINATE PROBLEM OF LEAVING EITHER PINS IN)

I do admit that this can not be done on large / wide body a/c.

If Company procedures are slack?

Should an ASR / EOR be filed?:sad:

[spannersatcx]

Used to handle Air Jamaica 340's and the pins they supplied joined with steel wire were a steering bypass disconnect pin and the nose leg downlock pin. We had to install both on arrival, and as they were joined with steel wire you had to remove both to show the crew you have removed them after pushback.

On our own a/c 747, 330, 340, 777 we only install the bypass pin.

p.s perrin stop shouting!:=

[Perrin]

Sorry to all, I found the caps lock key at last.
I see I have been proved wrong there are airlines that request downlock pins very surprised to hear it but will go with the flow.

[Aloon]

Ground lock pins?? As a tug driver ( limited knowledge! ) I will only tow empty 777 / 747 ( my main a/c ) with them in.

Perhaps it's the fact that the nose overhangs my cab???

Different airlines display different rules, but I can insist on them being IN if I'm responsible for the tow!!
Never a puchback though..... Onlt STEERING bypass......

I had a ' thing ' with a pilot who refused to put his beacon on before pushback, I said to him, ' then why is ground lock pins part of your before starts then?? ' He replied by saying that they were before engine start, not pushback... So he'd be happy to find ground lock pins missing during the push.. I think not.. And the catering truck imbeded in his tail??? MAD boy he was!!!!

[celtic mech]

According to Airbus Maintenance Manual, it is NOT necessary to install Lock pin if the a/c is doing a pushback for flight. Is is only necessary to instal the pin of we are towing the a/c. Airbus say it is optional to instal the pin for a regular pushback.
Having said this, my company use the Downlock pin on pushback for the 330's, for the simply reason that its attached to the bypass pin by a connecting wire. there are Remove Before Flight streamers on both pins. Its just the belt and braces method. Whats the harm. Its little or no hassle removing the Lock pin from the 330. And as they are both attaced to each other, it is virtually impossible to forget to remove them both.
A few years back our companies Engineering Dept sent Query Notes to Airbus and Boeing asking them the question Are Downlock pins required for pushback in relation to positioning the a/c for flight. Both Replied with NO. only the steering bypass pin is required.
I heard lately that a certain airlines flight out of DXB, the captain refused to allow the a/c to be pushed back without the Nose downlock installed!! He delayed the a/c departure. Turned out he was in the wrong. company MOE stated only bypass needed and this was of course stated in the M.M. also. Suppose he was just used to seeing us display both pins on pushback as we use them both out of habit.

[Aloon]

Out of interest.. Does anyone use a steering bypass pin during a startup only??? For their own safety??? Just to ensure the flight deck have something to look at to ensure ground crew are clear???? Do cockpits have an indication of this system being bypassed????

[celtic mech]

On the airbus, you indeed get an ECAM message saying the steering is bypassed when the pin is installed. If you look at this, it is a green message without engines running. when engines are started, this then turns amber for the simple reason of alerting the crew so as not to depart with it installed.

[Aloon]

Cheers 'Celtic Mech'....

Would like to know of other a/c in relation to the question...

[virginpaul]

BCAL: DC10 had a hockey stick downlock pin with a steering bypass pin on a chain - both used for pushbacks and towing. On 747 and A310 A320, used only bypass pin for pushbacks, downlock pin inserted (with open log book entry) for tows. On 1-11 - no pins for pushbacks but sys 2(?) hyd pump off during eng start, downlock pin inserted (with open log book entry) for tows.

My current co (not hard to work out who that is then):
747 - only bypass pin for pushbacks, downlock pin inserted (with open log book entry) for tows (again - we have ground use only hocky stick types)
The aircraft carry thie own full compliment of gear pins.
A340 - only bypass pin for pushbacks, downlock pin inserted (with open log book entry) for tows.

The thinking behind any company that does not require downlock pins for push backs is - manufacturers advice! and that you are primarily driving the gear in the "extend" direction during the push (okay - not when the tug is slowing the aircraft, or when a slight "pull forward abeam XYZ" is required).
A tow is a prolonged force in the direction of gear downlock "breaking" and retraction.

Paul

[Torqueman]

After having read most of the replies. Some longer than others! :confused:

For push backs

Ground locks ....NO

Steering bypass pin....YES

The only time I'd tow with ground locks in is from line to the hanger, etc. Especially with APU problems. No hydraulics (although I wouldn't tow without brake accululator pressure just in case).

I know it's theoretically possible, but everthing is working to keep the gear down. It takes a great deal of force to get the nose gear up. You're working against hydraulics (3000 psi on Airbus) and downlock springs which lock the gear down in the event of freefall in flight.

The end :D