Is this a good reason for a high speed RTO?

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ahramin
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Re: Is this a good reason for a high speed RTO?

Post by ahramin »

tbaylx wrote:
Wed Dec 11, 2019 8:16 pm
valleyboy wrote:
Wed Dec 11, 2019 8:08 pm
Again I think people are taking issues out of context - "never say never" refers to anything can happen and how you react is not set in stone. Human factors are such a fluid thing. What you did today and how you reacted could be all together different under similar circumstances at another time depending on variables you are dealing with. I still standby the fuel dumping issue - if the aircraft is flying and safely under control do your drills and check lists and land. Fuel dumping to me is a save your ass procedure just like "radar or firewall" thrust.

I'm putting up the lash in respect for the horse. :mrgreen:
Theres a lot more risk in landing overweight than in dumping fuel. If you're above 4000' it evaporates in the air before reaching the ground. If its not a time sensitive emergency why would you not dump fuel to reduce landing weight, distance, brake energy requirements etc.
Why would you not dump fuel for every landing? There's always a little extra you could get rid of to reduce landing weight, distance, brake energy requirements etc.

The only reason for which I would consider dumping fuel is runway length requirement. Fuel costs money. Landing weight does not, landing distance does not, brake energy requirements do not. If there is a long enough runway to handle the current weight at the current conditions, our procedure is to land as per the overweight landing checklist which makes perfect sense.
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pelmet
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Re: Is this a good reason for a high speed RTO?

Post by pelmet »

I would be cautious about deciding not to dump unless runway limited. We landed once ten thousand pounds overweight in accordance with company policy. After convincing the captain to use the longer runway, we used up a lot more than expected, and would have had a problem if we had used the shorter one.

I suspect the mathematics of it all is that the increased energy required to stop is the square of the runway increased weight, or one of those kind of formulas where what was around a 5%weight increase required much more than 5% increase in braking energy. More weight combined with higher approach speed. And then you float a bit.

As for landing a few hundred pounds over max, once in a while, aside from the Twin Otter where it was a frequent event(as all Twin drivers know), I don’t remember that happening but I’m sure it did occasionally to some in the old days where no one ever found out. At the new company, also a new culture, and any broken limitation is a big deal and monitored, and you will be called upon for 100 pounds over max landing weight or a one knot over speed. And it does go on you record.

One crew even got in trouble for pushing back slightly above max taxi weight.
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ahramin
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Re: Is this a good reason for a high speed RTO?

Post by ahramin »

Expected from what? Best guess? TALPA ARC?
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valleyboy
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Re: Is this a good reason for a high speed RTO?

Post by valleyboy »

Possibly you could say I contradicted myself but I think I said or indicated that while I would never reject above V1 (I was always a fan of V1=Vr on bare and dry runways and heavy weights) but what I meant was want you would do and what you actually do on a particular day you can never be really sure of of your reaction until after the dust settles. I know we should never stray from our training but facts speak for themselves.

Fuel dumping in Europe for example can add up to 2 extra hours in the air because they want to send you out to the north sea if you are operating northern France and above. It's perfectly safe to land "heavy" and as I said there are aircraft (737-some models at least) that can't dump fuel. Of course in doing so besides the captain's decision maintenance and commercial ops are involved as well. Also I think a lot of my thinking comes from flying aircraft with more than just 2 engines. Ya I'm old and still think more engines is still better.
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AuxBatOn
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Re: Is this a good reason for a high speed RTO?

Post by AuxBatOn »

So, because some aircraft don’t have a system, it shouldn’t be used on all aircraft? Great logic...
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pelmet
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Re: Is this a good reason for a high speed RTO?

Post by pelmet »

I think the non-dumping aircraft are relegated to patient fuel burn procedures if it is decided to land at a significantly lighter weight. In the end, assuming that there is not a time critical situation lack of fuel dumping capability should not affect ones decision about whether to land at a lighter weight. It just means holding for a longer time.

Each situation is different. If on a very long runway for type and the company prefers an overweight landing, then it might make sense. I just suggest giving yourself some extra margin instead of accepting a landing performance anywhere close to the limit.
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digits_
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Re: Is this a good reason for a high speed RTO?

Post by digits_ »

pelmet wrote:
Wed Dec 11, 2019 10:07 pm

I suspect the mathematics of it all is that the increased energy required to stop is the square of the runway increased weight, or one of those kind of formulas where what was around a 5%weight increase required much more than 5% increase in braking energy. More weight combined with higher approach speed. And then you float a bit.
The energy you need to dissipate is the kinetic energy

Ek = (1/2) * m * v^2

If you are only concerned about the weight, then 5% increase in mass will result in 5% increase in landing roll (if the brakes can handle it)
If the 5% extra weight results in 5% extra speed, then a 5% increase in mass will result in a 16% increase in landing roll (if the brakes can handle it)
If you float due to the extra speed, the extra speed was probably not necessary though...
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pelmet
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Re: Is this a good reason for a high speed RTO?

Post by pelmet »

Thanks. Higher approach speeds go hand in hand with higher weight as we all know, so that ten thousand pounds over max landing weight on a narrow body jet is significant even if it doesn’t sound like too much.
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Re: Is this a good reason for a high speed RTO?

Post by AuxBatOn »

And brake energy requirements are not directly proportional to landing ground roll.
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co-joe
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Re: Is this a good reason for a high speed RTO?

Post by co-joe »

I would think that a 130 Kt RTO in a 763 would put you at risk for melting tire fuse plugs, wouldn't it? Did they have to wait for cool down before taxiing back to the gate? Did they get local ARFF to come put the IR camera on their brakes before taxxing? Just curious.
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