# Why are emergency vehicles needed for a runway excursion?

When passenger jets have a runway excursion incident such as this one in Birmingham it is apparently common practice to send emergency services vehicles to the aircraft.

Why are emergency services vehicles necessary?
I would think the plane is more than capable of getting back onto the Tarmac, so why doesn't it?

• It is more than capable of getting back onto the Tarmac - really? What makes you think that? – Simon Feb 22 '16 at 20:58
• What you can't see is the wheels on the grass buried up to the bogies. The wheels are relatively narrow and not designed for "off road" use. 45 tons of aircraft will quickly sink it. Even if you could get enough power to move it, the manoeuvre will almost certainly cause a twisting moment on the undercarriage which it is just not designed to handle. Even assuming no twisting, the sudden lurch as it freed itself would likely damage the nose leg. I've seen a heavy jet on the grass. The only way to move it is to tow it. – Simon Feb 22 '16 at 21:28
• Here you can see how buried the wheels were. To answer your question about emergency services, imagine an hydraulic line had split and sprayed oil onto the hot brakes (it had just landed, and this has happened before). A fire starts. If the emergency services had not deployed, what would your question be now? – Simon Feb 22 '16 at 21:36
• In addition to the above, most of the equipment in that photo is airport based. They exist literally for this type of work - why WOULDN'T you use caution and involve them? – Dan Feb 22 '16 at 21:41
• @Dan Exactly. You have people trained in dealing with aircraft emergencies just sitting there. You might as well have them next to the aircraft instead of sipping tea on the other side of the field. – Zach Lipton Feb 22 '16 at 23:10

Why are emergency service vehicles necessary?

Something might have been damaged. What if something was and there is a fuel leak somewhere? Hydraulic leaks are also dangerous, and more likely as hydraulic lines run to the brakes and nose wheel steering. Better safe than sorry, so emergency services go check.

Sometimes, they also disembark passengers via the ladder if it looks like towing the aircraft to terminal will take too long and the aircraft is on unpaved surface where the mobile stairs have trouble going.

They can also help with moving the plane, especially on smaller airports that only have one runway and so have to close until the plane is moved away anyway.

I would think the plane is more than capable of getting back onto the Tarmac, so why doesn't it?

No, it isn't. Aircraft not designed for unpaved surface will usually sink in somewhat, especially if the ground is wet, and require a lot of power to pull out. Sometimes, the tow truck is enough to get it out, sometimes they have to put planks under the wheels and sometimes they have to get out hydraulic jacks or inflatable support bags.

Even if the plane did not dig in and is easy to move, providing the power with the engines is not a smart thing to do, because the engines will throw up dirt and stones that could damage them, other parts of the aircraft, or something else around. Tow truck is much better for that job.

Going off the the runway can be pretty rough. It not unlikely that a passenger got injured or part of the plane got damaged.

Going full throttle on the jets will rip up the dirt and grass and fling it everywhere. It will also put quite a bit of force onto the landing gear which already got a beating from going into the grass.

Much safer to tow it back. You can see the white towing vehicle in front of the plane.

• And even if the risk of someone being injured wasn't likely, you already have the emergency vehicles available so you lose nothing by sending them. Best case: Your crews get an impromptu drill and something to make their day more interesting. Worst case: you need them there ASAP as the aircraft bursts into flames. Either way, there's no downside to sending the emergency services instantly. – Jon Story Feb 25 '16 at 16:31