Tire Failure on Takeoff - 747

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If a tire blew at V1, it's actually markedly more dangerous to abort than it is to continue the takeoff, get a box pattern, work on a plan and land.

Blowing a tire doesn't render a aircraft unflyable near V1. But a botched high speed abort has severe consequences!

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Amen.

Reference "When Mr Murphy Rides your Jumpseat" in the Aviation Safety Symposium.

Nearly everything you'd like to know, addressed in that article.
 
Some people talk about three different phases of takeoff, not really in reference to the issue at hand, but some folks talk about what they'll abort for at or before 80 knots, and then the thing that they'll abort for prior to V1. But at V1, with a flyable aircraft, engine fire or failure, in a very general sense, it's far safer to launch, bring it back around and land than it is to risk blowing tires, oveheating brakes and sliding off the running off the runway at 150 knots into a fence or embankment.

At least in the MD-88/90, if the thrust reversers don't actuate the autospoilers, which in turn activates the RTO (rejected takeoff) mode on the autobrakes as expected, the precious time you waste in realizing that you're 'full manual', you're probably already off the runway. And a simple 'whoops, one of the cargo doors indicates open, we'll run the procedure and make a reasoned decision' becomes a flaming ball at the end of the runway.
 
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Some people talk about three different phases of takeoff, not really in reference to the issue at hand, but some folks talk about what they'll abort for at or before 80 knots, and then the thing that they'll abort for prior to V1. But at V1, with a flyable aircraft, engine fire or failure, in a very general sense, it's far safer to launch, bring it back around and land than it is to risk blowing tires, oveheating brakes and sliding off the running off the runway at 150 knots into a fence or embankment.



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We use the same thing, but with 100 knots as the "abort-for-all" speed when under, and over 100 knots it depends, up to refusal. Beyond Refusal we're generally a go depending on the circumstance, but that's only because we have a drag chute, a tailhook, and a couple of cables to catch before the runway as well as a net barrier in the overrun. But apart from that, with no arrestment gear, beyond Refusal (V1 for civvies), it's a go.

Where we have a questionable situation is in what's known as Category 3 takeoff ops with no arresting gear. That's where Critical Field Length exceeds actual Runway Length, and Decision Speed exceeds Refusal Speed....ie- too fast to abort, too slow to takeoff yet. Probably the nylon-letdown becomes a good option here.
 
Another consideration for us bus-driver types is evacuation. If you've got to do an evacuation, you will have injuries, without a doubt. High speed aborts for things that don't render the aircraft unflyable are going to probably end up in having to egress the aircraft if things don't work perfectly.

I used the 'door ajar near v1' example because it's not that big of a deal. Most aircraft will fly perfectly with a door open. If you take the aircraft airborne, run the non-normal procedures checklist and it's determined that the aircraft is pressurizing, chances are that the door is fine and you can make a decision from there. But if the aircraft isn't pressurizing, it's ajar and you've got another set of decisions to make.

But in that case it's better to make that decision while making turns in a box pattern above MVA with the autopilot on rather than in the last few seconds before rotation.
 
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Another consideration for us bus-driver types is evacuation. If you've got to do an evacuation, you will have injuries, without a doubt. High speed aborts for things that don't render the aircraft unflyable are going to probably end up in having to egress the aircraft if things don't work perfectly.

I used the 'door ajar near v1' example because it's not that big of a deal. Most aircraft will fly perfectly with a door open. If you take the aircraft airborne, run the non-normal procedures checklist and it's determined that the aircraft is pressurizing, chances are that the door is fine and you can make a decision from there. But if the aircraft isn't pressurizing, it's ajar and you've got another set of decisions to make.

But in that case it's better to make that decision while making turns in a box pattern above MVA with the autopilot on rather than in the last few seconds before rotation.

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Agree. One of the situations they love to give in the sim is a Master Caution light about 5 knots prior to refusal (about 165 or so knots, depending). With the MC light, you have to look down at the caution/warning panel to determine what it is, unless it's a fire switchlight, which is located next to the MC. More often than not, it's usually the "IFF (transponder) inop" caution light, and guys will end up aborting, blow a tire, get the drag chute that becomes a streamer, drop the hook which bounces over all the arresting cables, on the runway that has the departure-end barrier NOTAMd out of service, and the ejection seat made by the lowest bidder that's outside it's warranty that day......ending up as a "smoking hole" beyond the departure end.
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Being an ergonomic disaster, the 117 is tough as a single-seat bird, since for hydraulic emergencies, you'll get the MC, to where you have to check the caution/warning panel, which is the asterick-marked caution/warning lights are lit for HYD, you need to look at a third panel located on the other side of the cockpit and slightly behind you, to determine if it's one of the one's that will render the plane unflyable..............and you're usually given this one at refusal too!

Sometime I want to strangle the sim instructors............
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Damn sim instructors - always wanting to come up with a Kobayashi Maru type scenario.

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Can't you just re-program the sim to cheat?
 
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Is this section now off limits from posting???

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Shouldn't be. Chime in, my friend!
 
> One of the situations they love to give in the sim is a Master Caution light about 5 knots prior to refusal

On the LearJet 45 all but the most critical alerts are disabled during critical phases of flight, i.e. take off roll and just before landing. So we don't have that problem
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This might be a stupid question but how do you know that a tire has blown on such a large plane??

Can you feel 2 tires blow?
Are their TPM sensors in the wheels?
Is it dangerous to retract the landing gear with blown tires?
 
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Can you feel 2 tires blow?

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I'm sure you can. I can hear the nosegear roll over the individual runway centerline stripes and especially the recessed lighting so I think a blown tire would be pretty obvious.

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Are their TPM sensors in the wheels?

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Not in the super-stretch EFIS DC-9!

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Is it dangerous to retract the landing gear with blown tires?

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Yup!
 
Cool thanks for the answers Doug.

Just a side note: I was on the freeway today driving next to Semi-Truck. I look over and see that one of the rear tires on his trailer is complete blown to shreds. I try to motion to him that his tire is blown and he just ignores me. Funny to think that a 747 could feel two blown tires when this truck driver had no idea that his tire trailer tire was just about missing.
 
Plus, if you ask any Concorde pilot, blow outs can be fatal. I think there was also a story of a DC-8 or 707 in Africa that blew a tire which resulted in a fire in the wheel well after gear retraction that killed everyone on board. I can't remember the specifics, but it was something that we talked about in aviation safety in college.
 
The 747 has tire pressure monitors as well as brake temps, as do all the other widebodies I'm familiar with. I'm sure the 74-400, like the MD11 and several others, has an aural "tire failure" alert as well. Our aural portion in inhibited at the higher speeds until after 400'.
 
If you are interested in this sort of thing, you should check out the 'Takeoff Safety Training Aid' which can be found at www.bluecoat.org. It was developed by the FAA a number of years ago after a series of accidents due to high speed aborts. It is relatively easy reading and contains a lot of good information. If you fly a jet, you really should read it.
 
I think the DC-8 (or 707) that put the gear up while it was on fire was in the Middle East somewhere.

MikeD - I thought if you had a tire blow over 45 knots you would just eject?? Isn't that your get out of jail free card? In the slighest distress safely eject, walk back to the flight line and try again?
 
Safely eject, and come out an inch shorter each time. If I remember correctly, you medical out with something like three ejections in your career due to the stress on your spine.
 
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