Northwest DC9 vs. pushback truck

[EmDeer]

Found this on Airliners.net. Does anybody know the story of this incident?
http://www.airliners.net/open.file?id=1171294&size=L

[Longtimer]

Feb 5, 2007 1:28 pm US/Central

Tug Collides With NWA Airplane At MSP
(WCCO) Minneapolis A Northwest Airlines DC-9 aircraft was damaged when it was struck by the tug vehicle pulling it, according to airline authorities.

According to an NWA spokesperson, the tug came loose and slid underneath the plane, sending the nose of the aircraft into the air and damaging it "significantly."

No passengers were on the plane at the time of the accident.

The accident happened at the end of the E concourse.

The tug driver was injured in the collision, but authorities said his injuries were not life-threatening.

[HZ123]

That sounds unlikely because surely if it had come loose it would have taken the nose wheel out. Looks more like a vacancy for a tug driver.

[Blues&twos]

How about if it "came loose" whilst turning right? The tug would have been clear of the nosewheel, the a/c momentum causing it to run over the tug?

Having said that, you'd have thought that if it had been turning, the tug would have been off to one side rather than central under the fuselage....:confused:

Back to the drawing board.

[srs what?]

Looks to me like a towbarless tug, i.e it scoops the nosewheel up, in which case if it was actually involved in pushing the aircraft back the cab would be 180o to where it ended up. In other words it looks like this tug was just driving towards the aircraft.

Hope that makes sense.:confused:

[limey lad]

Yes, it was a towbarless "supertug". The DC9 was being moved from the hangars to a gate when this happened, and I think it was being turned into a gate towards the end of the E-concourse. This would take 5 minutes or so to accomplish based on the speed of these supertugs. Conditions were freekin' cold with temperatures around -5 deg F with a stiff wind out of the northwest giving a windchill factor of around -20 deg F. This is very cold even for MSP in the midst of a cold spell. Ramp conditions were basically clear and dry with some icy patches.
NWA have only this last year or so begun using these super-expensive supertugs in MSP. They have also this last year changed from having Mechanics tug the aircraft around to having trained Ground Service Personnel perform this task. Of course they also have someone in the cockpit during these tows.

[Oshkosh George]

Pretty serious for the aircraft,as they are to part it out,in america- speak! Economic write-off.

[clicker]

I wonder of the brakes were applied on the DC-9 and whats the yellow item on the ground where the nosewheel would have been?

With the skin damage it looks like the aircraft has come to a stop, the tug has continued on causing the nose to lift allowing the tug to ride underneath.

[PAXboy]

With the skin damage it looks like the aircraft has come to a stop, the tug has continued on causing the nose to lift allowing the tug to ride underneath.But the tug is facing the wrong way - it is pointing towards the tail.

If it had been pulling the a/c forward onto the stand (as mentioned earlier) then it looks as if that turn was to starboard. The tug has then pivoted almost 180 degrees. In ploughing under the belly, it has forced the fuselage up and the nosegear has been lifted straight out of the 'trap' that captures and holds it in the tug.

Supertugs always have the cab out in front, irrespective of whether they are pushing or pulling - the cab usually pivots. If the a/c had overrun the tug, then the gear would have been smashed and the tug still facing the direction of travel.

Conversely, if the DC-9 brakes had been applied with the tug still moving - then the gear would have been dragged backwards out of the hydraulic arms and the nose would have crashed down. The tug would still have been facing the direction of travel.

But the whole tug has pivoted from it's usual orientation and penetrated so far as to indicate that what went wrong happened very quickly indeed. It look as if the tug has pivoted around the nosegear to face astern.

One might conjecture that a failure of the tug's drive train caused one side to go forward and one in reverse, or one side to lock. With the huge torque on an icy tarmac, the tug would then spin on the spot in the blink of an eye. It would smash into the belly, lifting it up and the nosewheel would pop out of the trap. The driver would have had no time to react.

I hope that someone will publish the report in due course.

[Fargoo]

The nose wheels tell the story. They self centre when the nose is in the air - here they have turned almost 180.
Looks to me like the tug has braked on an icy patch and been spun around to starboard until underneath the aircraft. Aircraft has then continued forwards up and over the tug pulling the nose wheels free of the tug.

[clicker]

Thanks PAXboy,

As you may have gathered I have no working knowledge of supertugs.

Your theory sounds a darn sight better than mine, might also explain the gashes.

Cheers Clicker

[PAXboy]

Let me say that I have no experience of operating tugs, my view is based on observation of airports for 40 years. Whether the tug had a failure of the drive train or not - ice seems likely to have been a key factor. I hope the driver is able to return to work ere long.

[Swedish Steve]

There was a very similar incident at ARN two years ago. TBL tractor towing a Finnair MD80 on an icy ramp tried to turn when going to fast. The aircraft overtook the tractor which became stuck in the fuselage side. But our tractor kept a grip on the nosewheels.
The problem with TBLs is that they are very light. There is no added mass like you get on old type tractors.

It is standard practice when using a TBL for towing to have NOBODY on board. You don't need a brake man. The only reason for having someone on board is if you need the APU running to power the nav lights at night. At LHR, BAs TBLs all have generators fitted to supply power to the aircraft. We use a van with beacons following the aircraft.

The moral of the storey is that when towing with a TBL in the winter take it easy.

[Ignition Override]

An Instructor at NWA told me that the de-icers only sprayed ONE of a DC-9 jet's two wings at FSD, Sioux Falls, S.D this winter! Apparently the passengers paid attention and prevented what could have easily been a crash.

A very senior lady Check Airman was the Captain on a different flight where the de-ice crew was planning to check the upper wing (surface) with a wand, to see if cold fuel in the wing tanks caused any clear ice to form on the rough stripes. Well, the de-ice crew told the flightcrew that a wand was stuck in the elevator. They thought that the t-tail, being higher than the wings, was the upper wing! Her name is L-.

Outsourcing at its best. But the price is always right. The brilliant leadership at NWA apparently laid off a very large number of senior ramp personnel this fall. Airlines are very well-insured against a hull loss-whether your family is onboard or not.

[Heiko Bukovac]

We had a similar incident in EDDF. A tug pushed a RG-MD 11 too far of an angle which caused the hydraulic-hose to break. The tug slid on the oil and turned right underneath the aircraft causing the wheel to collapse. Not a pretty sight.

[Halfnut]

Looking at the nose gear that is the ground shift linkage you see located on the forward portion of the nose gear strut. When the aircraft came down the assembly line in Long Beach Mickey D installed it on the backside. This tells me the nose gear did swing around 180 degrees. How the Super Tug got where it is I don’t know but the nose gear is 180 degrees out of phase.

D’oh!

[PAXboy]

Since the tug is also nearly 180 degrees out of phase, that would make sense. That it was twisted around as the tug spun about the vertical axis of the nose gear, until the rising nose lifted it out. The lack of other damage to the gear indicates that the alignment of the gear in the tug's grip was not altered.

[MD80rookie]

The DC-9's and MD's are REALLY tail heavy when empty. Could it have been a imbalance problem? Still doesn't explain the tug's position though.