Why Mechanics Should Think Twice about Taxiing Aircraft

 Seeing the Southwest 737 in the mud at Orlando International Airport with a broken nose landing gear this past week reminded me why I think mechanics should think twice about taxiing aircraft for maintenance.  Let me say, that I have no idea why the 737 ended up in the mud on its way to a maintenance hangar – could have been anything from bad hydraulics to bad taxiing – but we’re likely to never know because the NTSB has refused to investigate.  According to news reports, the NTSB declined to investigate considering the incident a maintenance-related issue that did not have safety of flight implications. I disagree with the NTSB’s decision not to investigate at all.  How does it know there were no safety of flight issues if it doesn’t even do an on-sight assessment of what happened?

Maybe the FAA will investigate but it’s unlikely that any finding will be made public.  And if only the company does the investigation, we know it won’t be made public.  Which is unfortunate for the maintenance community because these investigation reports help us learn what happened so we can prevent similar incidents in the future.

Nonetheless, the incident reminded me why I think it’s generally a better idea to tow aircraft for maintenance than to have mechanics taxi them.  Taxiing aircraft – especially modern airplanes with high bypass engines – requires considerably more skill and practice than was necessary in the past.  These airplanes, with low fuel, no passengers and no cargo, can move quite fast even with the throttles set at idle power.  This requires a constant application of the brakes to keep the aircraft taxiing slowly enough to meet standards which are generally stated as equivalent to a fast walk. 

Maintaining such a relatively slow pace is tough with the usual airport pressure to keep things moving and even the occasional urging from air traffic control to expedite clearing the area.   Mechanics taxiing aircraft have to monitor aircraft systems, particularly hydraulics, maintain radio communications with ground control and constantly scan for aircraft, vehicles and other obstacles.  Just because ground control says you’re cleared to taxi, of course, doesn’t mean that you can be any less vigilant for potential hazards. 

So while there are risks from towing aircraft, I believe that generally they are less than when mechanics taxi because they can more fully concentrate on their surroundings.   I am reminded of when Logan Airport decided to ban aircraft taxiing for maintenance for noise reasons.  Although the ban was not intended to reduce ground damage, anecdotally, it was reported to me that it had a noticeable impact on ground damage reduction.

Although, I believe that towing aircraft is generally a lower risk than taxiing, it may not always be feasible to tow an aircraft for maintenance.  In those situations, only mechanics with proper training and experience should be used.  And emphasis needs to be placed on all the critical pieces of safe taxiing – maintaining proper speed, monitoring hydraulics, maintaining radio contact and scanning for obstacles.

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So we are too stupid to taxi aircraft now?

I do not know who wrote this post, but I must agree with all of it. (I'm sorry that "Stupid Mechanic" may feel a bit insulted and I understand. Taxi authorization is a worthy and impressive add-on for any A&P and I have no wish to diminish any A&P's skill or worth under any circumstances. Never!!)
That said, the unknown author makes valid points throughout. Taxi for maintenance is a slow, cumbersome process, often with limited visibility and conducted by folks who, by the very nature of their regular work, may not be absolute experts. Fully commanding and operating all of the required safety systems, watching for threats yet not always knowing where it come from,communicating with ground control and other tasks, could well be a safety stretch for some A&Ps. Why take the risk?
I do not know the facts here, but I cannot imagine that towing a for-service aircraft is more costly than spinning at least one, big-bore jet engine. Towing has to be less costly, even with two souls on the tug and at least one (or none?) on the flight deck. In addition, the two operating the tug are far better positioned to seen and to anticipate potential conflicts or threats: they CAN see better than anyone on the flight deck. I've already mentioned cost.
I won't suggest banning all taxi operations by A&P staff; there may be some excellent reasons to maintain some as permitted taxi operators. But, for the vast majority of maintenance required moves, a tug-powered operation, with necessary staff, just smells a whole lot safer and even less expensive.
I'm sure that I'll get flamed, blamed and blasted for speaking up, but when you do, please gentlemen, please try to help me understand WHY I may be in error. If there are legitimate reasons for pre/post maintenance moves to be made with an A&P driving a self-powered airplane, **Please explain** the circumstances; I'd really like to know.
I'm not an A&P, do not play one on TV, yet have great respect for friends and others who are. I still do not understand why self-powered taxi operations are important to the profession, the Special Ticket and ego part aside. Those too are important to some of the individuals concerned, but are they essential functions? Are they genuinely safe functions? I Hope someone will answer and explain the questions to a genuine knuckle-head. Please... Think first and then write, to explain why a different view is a safer, more efficient view. Thank you, guys (and gals). What am I missing?

Seems so, pathetic really, I could cite many cases of smashed up aircraft sitting off the runways or all over the countryside, perhaps we should ban pilots from flying them as well, that should clear that problem right up.

While I agree that a person needs to be trained and experienced, there are valid reasons for taxiing and run-ups prior to inputting for maintenance. One good policy is to have two techs in the cockpit. The other part is your advice is obviously directed toward "big" airports and "Big" aircraft. Frankly, I have seen more issues and aircraft damage done by ground crews towing aircraft than by techs taxiing.

Author is John Goglia

Whenever a post inspection engine run has to be performed as required by 14 CFR part 43.15. We routinely taxi the aircraft to verify proper function of several other things such steering, braking, turn coordinator, DG, HSI, compass etc. These checks would be difficult to make without taxiing the aircraft.

For larger aircraft which require periodic compass swings, or brake burn-in, the same applies.

To me taxiing is just another operation that requires a procedure, and adherence to it. I see it as far less risky than many of the tasks that an A&P is authorized to perform.

One of the most overlooked items that I have personally seen with regard to taxi operations, is a clear understanding of airport movement area markings, signs, and ATC procedures.

I too like the idea of two personnel on the flight deck at all times. One concentrates inside while the other outside. It is a must at my place whether a C172 or Lear 45.

I do agree with the initial post about this however...............Mechanics should always think at least twice about everything we do, to ensure that we know what we are doing before we do it, and that it is in the best interests of all concerned.

Doug Hereford

There are valid points from both sides! The sizes of the aircraft only differ in the $$$ amount of damage. It happens in GA, Corporate, airlines and ,yes, even the military. To be politically correct, feces occurs...

Doug hit the nail on the head when he said "...taxiing is just another operation that requires a procedure, and adherence to it."

I would add three things to that thought, CHECKLIST, CHECKLIST and CHECKLIST. Like the American Express card, you don't leave home without it!

Without doubt a worthy discussion which is being repeated on several other channels.

Two words jump out at me however; a) checklist and b) hydraulics

When I took my first B727 for a spin as a new A&P many years ago, we ran through the checklist (thanks to my partner at the time) and had a thorough understanding of what we would do if things went haywire.

I don't take the big birds out much anymore, but sometimes I'll ride along with other techs and I'm surprised how often checklists are ignored. I can *totally* understand the mind-blanking scenario that occurs when one realizes all of a sudden that the brakes aren't doing what they're supposed to....