Ask The Pilot

[jb747]

But in the case of CNS, wouldn’t taking the full length get you airborne 500m earlier and a little more altitude and terrain clearance if needed? And possibly also get you into the turn slightly sooner?

If you didn't run the numbers for the correct length (but used the ones from the intersection), then yes, you'd get airborne earlier. But you wouldn't be using the correct derate, nor would the abort calculation be correct. If you ran it (the calculation) for the full length, you may end up with even more derate, and would still get airborne at the same point. AV might feel like playing with the actual numbers. From memory the turn was at the end of the runway, so you might be a bit higher, but not a great deal. Terrain isn't actually an issue as long as you follow the procedure. You could remain at 100' and you'd still miss everything. You don't want to be in the turn sooner. It's based on the correct starting point (end of runway) and 15º of bank. When you roll out, you're on a nice, safe track.

 

[AviatorInsight]

I've been flying in and out of Cairns for over 50 years now and I'm pretty sure that we used to occasionally depart from 15 straight down the coastal corridor between the Bellenden Ker and Murray Prior ranges, given the weather conditions being suitable. There is only a slight jink in the valley before the terrain opens up at Cowley. No sharp left turn required and no possible late turn concerns.

As a single aisle passenger I'd prefer that option if the aircraft was experiencing something like what QF520 did last week. Not that my opinion would matter in any way.

On another CNS matter. It's not that long ago that intersection departures used to be the exception. Not any longer. I'm always happier to turn right and back-track a bit for the extra four or five hundred metres.

But in the case of CNS, wouldn’t taking the full length get you airborne 500m earlier and a little more altitude and terrain clearance if needed? And possibly also get you into the turn slightly sooner?

I can definitely see where you're coming from. I would prefer to turn away from high terrain at all costs if the aircraft was still flying well. Over the ocean if gives us a lot more room to fly around. However, until there is some sort of controllability issue, I'd rather not fly up through a valley at low level with possible environmental effects and giving myself a much tighter envelope to fly in while trouble shooting.

The missed approach for the RNP (A GPS based approach) to runway 15 will take us through the valley. But I would have started that manoeuvre from 680ft and 2 miles before the start of runway 15 with 2 engines doing at least 1000fpm in the climb. Very different scenario.

If I take the numbers (24K engines) from the intersection vs the full length, I get almost the exact same V Speeds (V1 is 141kts at B2 vs 142kts at full length). The major difference is the thrust (91.3 at full length vs 93.8 at the intersection) and assumed temperature.

So we would actually be conserving the engines by doing a full length departure. The take off point itself wouldn't make too much of a difference in terms of getting airborne quicker because I effectively have less thrust available to me.

If I was to change that and use full thrust (26K engines) from the full length I get an N1 of 98% and V speeds of 138 (V1), 140 (Vr), 148 (V2). So in this case, yes I would get airborne earlier but now I'm not conserving the engines (not really my problem, I use what I need).

But I would argue here that the take off safety in a jet aircraft is more about the decision making at V1 (go/no go point) and less about the remaining runway available. In both cases the aircraft can accelerate towards V1 make a split decision to reject and then come to a complete stop on the available runway remaining.

We are not going to get airborne and then land back on the same runway with the distance available (even at full length).

As QF520 has shown, it can actually be safer to get the aircraft in the air (it is still safe to fly), secure it properly, give yourself and the airport plenty of time to come together to create a plan and then execute it.

So, is an intersection departure riskier? Not necessarily, from the figures above. What it does do is allow the flow of an airport to be even better and get aircraft departing quicker which is appreciative in a domestic environment.

 

[flyingfan]

Pilots, if you were in charge of designing the sim sessions, what if anything would you change about them - do they sufficiently train in dealing with serious problems or are they inherently limited?

Also, reading the sims are heavily booked and in use 24/7... does that inadvertently or otherwise cause pilots to get into the wee hours where a lot of flying (and potentially fatigue-related problems) happens?

 

[AviatorInsight]

Pilots, if you were in charge of designing the sim sessions, what if anything would you change about them - do they sufficiently train in dealing with serious problems or are they inherently limited?

Also, reading the sims are heavily booked and in use 24/7... does that inadvertently or otherwise cause pilots to get into the wee hours where a lot of flying (and potentially fatigue-related problems) happens?

The focus has definitely moved from a heavy checking environment to a training one. This is a really good thing in my opinion as it's relaxing crew a lot more. The idea is that we are just rocking up to work like any other day. So really anything can happen on any given day.

Know your memory items and limitations. Get the aircraft on the ground safely and then let's have a look at how it could have been done better/efficiently, etc. I would like more of that sort of thing for FOs to have a go at running and the Captain to be supporting to help prepare for a command.

Cyclic Sim sessions (checks) are not done back of the clock. Those are only reserved for training slots.

 

[flydoc]

But I would argue here that the take off safety in a jet aircraft is more about the decision making at V1 (go/no go point) and less about the remaining runway available. In both cases the aircraft can accelerate towards V1 make a split decision to reject and then come to a complete stop on the available runway remaining.

So, is an intersection departure riskier? Not necessarily, from the figures above. What it does do is allow the flow of an airport to be even better and get aircraft departing quicker which is appreciative in a domestic environment.

Great explanation @AviatorInsight, thankyou. How/does the full length/intersection departure scenario vary in the single engine context, vs the multi that you’ve described?

 

[Saab34]

When ‘V1’ is announced, is there a time period when the decision to go/no go needs to be made, probably more the no go? Ie 1 or 2 seconds?

 

[jb747]

When ‘V1’ is announced, is there a time period when the decision to go/no go needs to be made, probably more the no go? Ie 1 or 2 seconds?

There is no actual decision to be made at V1. It's simply a call telling you that the abort option is no longer available, and that you will now continue with any issues. When you hear V1, you remove your hand from the throttles, and from that point you'll continue unless you deem the aircraft completely unflyable.

If I recall correctly, the distance calculation for an abort allows one second for the actual decision.

 

[AviatorInsight]

When ‘V1’ is announced, is there a time period when the decision to go/no go needs to be made, probably more the no go? Ie 1 or 2 seconds?

I tried to be very careful in my wording that the decision is actually made just prior to. If you haven’t applied the brakes by the time you’ve reached V1, then you have made your decision to continue.

I thought it was 1 second for the aircraft to get into the reject configuration and then another 1 second buffer. Any longer than that and the aircraft will go off the end.

Great explanation, thankyou. How/does the full length/intersection departure scenario vary in the single engine context, vs the multi that you’ve described?

Do you mean as a single engine aircraft vs a multi one?

Then that one is an easier decision. In a single engine there is no V1 a decision is being made for you. I would always opt for the full length unless it was something ridiculous like a 3000m+ runway.

In that case, I would accept a 500m loss because I was confident I still would have runway ahead in the event of an engine failure and/or still have some altitude for a safe landing elsewhere.

 

[RSD]

As QF520 has shown, it can actually be safer to get the aircraft in the air (it is still safe to fly), secure it properly, give yourself and the airport plenty of time to come together to create a plan and then execute it.

That HondaJet in the U.S. about 5-7 days ago showed how aborting takeoff after V1 usually doesn't end well. The investigation report for that one will be an interesting read. The really short version for those that haven't seen the youtube videos is that for unknown reasons a Hondajet aborted takeoff when doing about 20 knots above V1 and ended up hitting a car on a road outside the airport - all four passengers and a motorist died, pilot survived.

 

[Cynicor]

Any thoughts about the various Indonesian carriers still flying through the Ash cloud while VA and JQ have stopped flights? Is there more to this than just “those LCCs are dodgy”? I wouldn’t have thought a pilot anywhere would value the job more than life?

 

[RooFlyer]

Speaking of running off the end of the runway, what became of the concept of placing a length of crushable material at the end as an arrester should the aircraft go off the end of the paved runway? Is it in place anywhere in Australia or on, say, the routes AFFers might commonly fly to?

 

[jb747]

Any thoughts about the various Indonesian carriers still flying through the Ash cloud while VA and JQ have stopped flights? Is there more to this than just “those LCCs are dodgy”? I wouldn’t have thought a pilot anywhere would value the job more than life?

Well, Jetstar are pretty dodgy, but I guess you don't mean them.

The Indonesians may not have an appetite for shutting down a major part of their air transport system, which would increase the risk they're prepared to bear. Nobody is knowingly going to fly into the main ash cloud, but the finer ash is everywhere (rather like our bushfire smoke) and that's the one where the variation in risk assessment will exist.

Beyond that though, they're pretty dodgy.

 

[markis10]

Speaking of running off the end of the runway, what became of the concept of placing a length of crushable material at the end as an arrester should the aircraft go off the end of the paved runway? Is it in place anywhere in Australia or on, say, the routes AFFers might commonly fly to?

Probably one for the “ask the airport engineer” thread
What you are describing is known as Engineered Material Arrestor System or EMAS. They are use in over 100 locales in the LOTFAP, and our nearest one AFAIK is at the threshold of Rwy 35L at HND. ZQN is currently getting one installed at the end of each runway.

https://www.faa.gov/newsroom/engineered-material-arresting-system-emas-0?newsId=13754

 

[NM]

Probably one for the “ask the airport engineer” thread
What you are describing is known as Engineered Material Arrestor System or EMAS. They are use in over 100 locales in the LOTFAP, and our nearest one AFAIK is at the threshold of Rwy 35L at HND. ZQN is currently getting one installed at the end of each runway.

https://www.faa.gov/newsroom/engineered-material-arresting-system-emas-0?newsId=13754

There is one at BKK, also known as Don Muang Golf Course

I do wonder how much evaluation of surrounding territory takes place as airports grow/expand and ground infrastructure (roads, buildings etc.) encroach on the airport perimeter.

Is this something pilots actually consider, either mentally, verbally or "I'll keep that option in the back of my mind" when planning departures and landings and flight deck briefings (pre-departure, landing)? I guess Lukla (LUA Tenzing-Hillary Airport) is one where second thoughts might prevail, with a stone wall greeting those who overshoot the landing, and a cliff drop at the end of the downhill runway for those not getting the takeoff right. Only a select few pilots get to operate there, of course.

And I guess one for @jb747 and possibly @Falcon 39 and @Buckshot10 - When waiting on the deck with catapult attached and ready for "launch", is V1 calculated/Defined? And is it 0kt or 1kt? And of course you definitely have a EMAS for the return.

 

[jb747]

There is one at BKK, also known as Don Muang Golf Course.

It was pretty ineffective.

I do wonder how much evaluation of surrounding territory takes place as airports grow/expand and ground infrastructure (roads, buildings etc.) encroach on the airport perimeter.

The system seems to be encroach, and then demand the airport close/change.

Is this something pilots actually consider, either mentally, verbally or "I'll keep that option in the back of my mind" when planning departures and landings and flight deck briefings (pre-departure, landing)?

We think about the terrain, but not so much what's built on it. Light aircraft people might keep roads or cleared areas in mind, but not much use or interest for the bigger aircraft. I guess Sully's use of the Hudson might count, but I dare say that he'd never have previously considered ditching there.

When waiting on the deck with catapult attached and ready for "launch", is V1 calculated/Defined? And is it 0kt or 1kt? And of course you definitely have a EMAS for the return.

There is no V1, when no options exist. Some aircaft would be able to fly away with the loss of an engine during the cat shot, and their pilots would be primed to jettison any stores, but it would very quickly be followed by ejection. Once that catapult fires, you're going.

V1 isn't the last speed at which you can abort after an engine failure, but it's actually the first speed from which you can continue the take off. In some cases of extremely long runways, it might be possible to abort from a higher speed, but we need that decision to be black and white, so any grey areas are ignored.

There can be a nominated rejection speed. For instance, I once flew on a KC135, way back before they were given modern engines. The aircraft was extremely heavy, and it was very hot. They had no V1 as we know it from airline ops. There was a refusal speed. The first speed at which they'd be able to fly away on 3 engines, was quite a bit faster than the refusal, leaving them with a gap when you'd be too fast to stop, but too slow to be able to accelerate and then fly away on 3.

 

[NM]

There can be a nominated rejection speed. For instance, I once flew on a KC135, way back before they were given modern engines. The aircraft was extremely heavy, and it was very hot. They had no V1 as we know it from airline ops. There was a refusal speed. The first speed at which they'd be able to fly away on 3 engines, was quite a bit faster than the refusal, leaving them with a gap when you'd be too fast to stop, but too slow to be able to accelerate and then fly away on 3.

Was that "gap" known as Vp (the prayer window)? Is it likely that same gap existed for the B707? Or did the KC135 have a higher MTOW? Did you ever see similar with the 747 Classic or would that have been deemed an unsuitable "mission" for a commercial operation?