Intersection Take-Off

[pointer41]

Question:

I travelled this week in the back of one of our carriers, JIA - CPT, rwy 03 departing. The aircraft took an intersection take-off.

Now, I have done a lot of such take-offs at one stage or another myself, and also heard a lot a debate on the issue. Granted not much runway was lost, but some was (as with my own cases, too.)

Wondering about it, I thought this place would be ideal to obtain some good gen from the community. So, what does the forum say? Opinions, por favor!

[dr27]

Saying goes "nothing as useless as the runway behind you and fuel in the bowser"...

In earlier days I would have had no hesitation in arguing that provided the calculations allowed it that there is nothing wrong with an intersection take-off but old age has made me more cautious and in less of a hurry and prefer to have all the runway available to me just in case...

Lets face it, it is preferable to abort and have plenty of time and bitumen left as opposed to aborting and having to slam on brakes and or reverse trust. Saver and easier on the equipement too.

[Kennel Keeper]

This is Africa where it is the norm to carry on excess hand baggage which no one weighs.

With wasted runway behind you its a fine time to find out your weight and balance is wrong and you need more tar!!

[George Tower]

It would be interesting to see from an economic point of view whether generally speaking it would be better to do intersection take-offs or derated take-offs. Presumably the intersection take-off might require higher power settings so you'd consume the fuel you'd save by sitting on the ground that bit longer, taking full length and using less power? Any drivers able to shed any light on how this works in practice.

Also I'd be interested to know what the general position is amongst the operators in SA with regard to use of reverse thrust. Many operators in the UK seem to have SOPs directing the use idle reverse only - apparently this yields big savings in maintenance.

Rgds

GT

[FO Gyro]

Max reverse thrust is used mainly to save on replacing brakes unnecessarily. Brake usage is high on aircraft on the domestic routes. Depending on the airline, some operators have a "power by the hour" agreement in place for the use of their powerplants. Not sure whether maintenance is factored into this, or if the operator pays for this.

Full thust take offs are avoided as a result to save some bucks, unless needed due to operational reasons. What it means is that the operator is not too concerned about increasing the engine's lifespan, but is more concerned about brake lifespans. It's always an economic juggle. SAA's A340's use a derated climb, also to save bucks. Apparently there is much to be saved in this phase of flight as well.

[pointer41]

Also, as I was not in the cockpit, I just realised a factor could have been traffic. We lost minimal runway as it was the last intersection, and could have been that ATC asked for an expeditious take-off.

What I'm really after, is company policies, SOPs and standpoints on the matter, as well as of course as the above, individual viewpoints.

One remains always a student in this game...;)

[FO Gyro]

ATC won't ask for an expeditious take off. It's normally up to the crew to request an intersection take off. Normally if it is the first flight of the day, we use full length to give the engines time to warm up properly on a cold winter's morning.

It is company policy to use intersection takeoffs as far as possible as it saves unnecessary taxi time, as well as extra brake usage. Intersection take offs are not allowed during low visibility takeoffs when Low Visibility Procedures (LVP's)are in force. For a wet runway, it generally is also not allowed.

What's gets me sometimes, especially in Cape Town is one asks for an intersection take off from ATC. They give it to you and sometimes you might end up waiting at the intersection holding point for some time if an aircraft is on final approach. Knowing this, they often won't alert one to the fact that there will be a slight delay, and would one not prefer full length instead. JNB ATC have caught onto this, but not Cape Town. I now say "Request intersection XXX, if no delay...". It seems to help a little. Cape Town ATC don't understand its pointless using an intersection if its not going to save you any taxi time. Any Cape Town ATC's to comment...

[reptile]

What I'm really after, is company policies, SOPs and standpoints on the matter...

Our company policy: Intersections may be used at any time, provided RTOW data is available for that specific intersection. We always aim to used maximum power reduction on take-off. If an intersection does not allow maximum power reduction, full length will be used instead. No intersection take-offs on contaminated runways.

Hope that helps.

[Goldfish Jack]

Quote "It is company policy to use intersection takeoffs as far as possible as it saves unnecessary taxi time, as well as extra brake usage..." unquote

Quote: "Cape Town ATC don't understand its pointless using an intersection if its not going to save you any taxi time." unquote

These 2 statements certainly seem to contradict themselves. You want to use an intersection to take-off and save on extra brake usage, but if you have to wait you want to taxi to the holding point and not save on extra brake usage??

Intersection take-offs are NOT initiated by the controllers but are asked for by the pilots themselves. They are not dependant of ATC input, but are requested when certain operational criteria are met within the cockpit and I was told taxi time was right at the very bottom of the queue, if at all.

As to waiting at the hold, I fail to see how it affects your operation if you wait at the intersection hold or the runway hold. After all it was the pilot that requests the intersection. If there is an a/c on final you are going to wait whether it is at the hold or the intersection.

There are often many factors which are beyond the aerodrome controllers control pertaining to when you can depart, ie traffic passing overhead, the a/c waiting to depart is early for their CTOT based on your AOBT, etc etc

I know from 20 odd years as an aerodrome controller many many pilots only request an intersection departure when the are taxiing to try and jump the queue which if you ask me is not very professional. The way I see it if you have to wait at the hold at least u are sitting waiting as opposed to using a lot more fuel to taxi all the way to the hold.

There are some times you are going to have to wait and that is a fact of flying. An interesting point from a colleague - he gets rilled when pilots ask for the intersection if no delay.... if seems they want to have their cake and eat it. (it seems to infer you want to have the intersection and be moved up to the front of the queuend why should they have a delay?)

[FO Gyro]

Goldfish. Let me explain it this way. Despite the way the performance figures are worked out, I don't think there is a single pilot out there that likes the idea of having runway behind him/her during an intersection takeoff. The philosophy of an intersection take-off is to save unnecessary taxi time. I can't think if any other reasons that are more important than this. My logic tells me that if I am going to have to wait, I might as well use the useless time sitting with the parking brake on and taxi to the end of the runway.

On most B737's, once they are taxing, the thrust is brought back to idle, so they use no more fuel to taxi or to sit with the parking brake on. Because the ground idle thrust is quite high, one normally has to keep braking during taxi, and this is the unnecessary brake usage I was refering to. Again, the pilot is not overly concerned about using some brakes, as opposed to having runway behind him, if there is a delay.

It's funny your comment about your colleague getting rilled if a pilot asks for an intersection "if no delay". He obviously does not understand the workings from our side. JNB ATC seem to be very good in this regard and often will tell you there will be delay from the intersection and asks if one would like full length. It's got nothing to do with jumping the queue. It's about getting the aircraft into the air asap so that we can make our schedule. What the ATC's need to realise is that the companies are rostering crew so tightly now within Flight and Duty, together with short aircraft turnarounds, the crew are often under some pressure to try and make up time when delays occur. Often these delays snowball as well.

Another gripe that gets me is that particularly out of DUR, if one is ready for start a few minutes early, DUR tower won't give start (which I understand comes from JNB) until the schedule is met, unless they can accomodate one early. If the crew have a short turnaround in JNB, they then fly a fast climb out and cruise, and guess what, they arrive in JNB at the same time had they started up slightly early and flown at normal speeds. To me a couple of minutes before start surely is not critical. What about the long haul flights? JNB ATC doesn't have a say when an aircraft on a 12 hour flight pushes back on the other side of the world slightly early. Whilst I realise the importance of flow control, slots, CTOT's, AOBT's etc, it just hinders the operation when one is ready, doors are closed and "the rules say" type of mindset prevails.

[Goldfish Jack]

FO Gyro

I am not in the mood to fight, get involved in any mud slinging, etc but what i suggest is you come and spend a few hours, not a turn around, in the centre and see the problems we have to put up with and then maybe you can see it from our side. I have not got the fingers to type a response to your reply, but do come and see what we have to do and how we do it. IF you ask us nicely we can set up the simulator for you and you can try your hand at controlling and see how to do it as well!

Then your perspective might change- if you have got problems then you should see what we have to put up with and then you realise you have got no problems at all. ATNS has gone to huge steps to accomodate the increase in traffic - the same cannot be said for ACSA - if the airports we better laid out and better designed to handle a/c we could move even more - remember delays are often put down to ATC when we have nothing to do with it. You only have to look at the layout of aprons in this country - 1 way in and 1 way out with no options. When you have third world airports with a first world ATC system you are heading for problems. Amongst other problems we have to consider is runway utilisation and occupation. Sure you get frustrated with us when we wont let u start, but have you also thought that sometimes we prefer to keep a/c in the bays, otherwise there will just be a traffic jam at the hold and I think (I might be wrong but I dont think so) most pilots would rather sit at the gate than at the hold burning fuel?

All i am going to say is if slots, CTOTs etc hinder your operation when you are ready, have you thought of the chaos that would happen if we just let anyone go when they wanted to and let them do what they want to do.

The important thing to realise about slots is that they are not ATC issued - they are issued by an IATA co-ordinating committee twice a year when all the airlines get together and discuss them - so if slots are a problem I suggest you take it up with your IATA co-ordinator. (ATNS has no input on slot allocation at all!) You might also like to spend some time with him/her seeing how they work the slot system. It might not be perfect but it sure reduces the peaks and troughs and makes a more even flow of traffic and together with Maestro will go a long way to making the system better and more ordered. What is Maestro you ask - come and visit the centre and see what it is! It is a good system and worth coming to the centre to see what/how it is.

Happy economic flying - it will be my pleasure to show you around the centre

[Shrike200]

Another informative and well-reasoned post from Goldfish Jack, as always. Quite frankly, having come from a contract background, I am continually impressed with the professional controlling we receive in SA. You only have to cross the border into Gabs to immediately see the difference.

On a thread related note, I heard a Skygod getting into yet another radio flurry at FAJS the other day when asking for an intersection take off. ATC told him to can the idea and join everybody else at the hold for 03L. He went to great pains to explain that 'we don't want to jump the queue, its ALL ABOUT THE GAS!!!'. ATC then said something which I didn't catch, to which the reply was 'No thanks, as long as the point's been made', or something like that. I didn't understand it at the time, since I reckoned he would have held either at the intersection or at the full length hold, and as somebody mentioned, we're all swanning around at idle thrust when taxiing anyway.

[FO Gyro]

Goldfish, why do forums like this have to be arguements? On the contrary I was trying to explain from our side why we use intersection take offs. It has nothing to do with jumping the queue, and perceived unprofessionalism and everything to do with trying to save some taxing time. That's my experience at least after 10 000hrs. The captain actually decides in the parking bay 20 minutes before start if he would like to use an intersection as part of our take off calculations. We request this before taxi before we can even see how many aircraft are at the holding point.

Besides its a Sunday. Peace be you with and you fellow ATC's that work in difficult situations. I will also refrain from using my "..if no delay" so that your colleague will no longer get "rilled".

[divinehover]

There are no safety issues involved in intersection take off's.

Before V1 you stop. After V1 you go. The calculated V1 speed will take the shortened runway into account. Extra runway is of no use to you as you are going to continue with the take off after V1. You are not going to ellect to stop after V1 because you think you might have some tar left. That would in fact be highly unproffesional.

Intersection take off's where correctly applied save time, brake wear, brake overheating(taxiing for 21R full length in JNB).

It's important to remember that you are not always field length limited. You can also be 2nd Seg climb limited, brake energy limited, Structural Weight limited.

All the finest airlines in the world use this option to provide flexibility to there operation.

Once again. There are no safety issues involved in intersection take off's if you understand the principles involved.

[knertius]

goldfish, things seem to be a bit different over here in the northern hemisphere. ATC WILL actually initiate an intersection take-off in order to assist with traffic flow. Especially in the case of a mixed prop and jet airport ATC will often want the prop to take an intersection in order for him to jump the que and not block traffic that´s behind him and possibly on the same departure route. i will often tell the FO to state on first contact with TWR or GND (depends on the airport) that we are ABLE for intersection X, Y or Z. ATC can then decide if they can use this info to THEIR advantage. If there is no advantage for anyone then they will usually say so and then i will usually elect to take full length. even if it might seem unprofessional to you to jump the que at the end of the day it might not be to the disadvantage of the guy ahead of me who has to wait anyway because the guy ahead of him is on the same SID (and i will then take-off during his waiting time) and the B767 behind me with very little extra fuel will actually be happy to see me take off earlier because i would have blocked him (me being a prop guy) if i had stayed in the que.
so, at the end of the day, the intersection take-offs do have their merit. at least over here they do...

[reptile]

goldfish, things seem to be a bit different over here in the northern hemisphere.........so, at the end of the day, the intersection take-offs do have their merit. at least over here they do......

"ATNS welcomes you to South Africa - For the correct time please wind your watch back 50 years." :E :E :E

[fluffyfan]

Goldfish, you say
I know from 20 odd years as an aerodrome controller many many pilots only request an intersection departure when the are taxiing to try and jump the queue which if you ask me is not very professional.
At the Airline I work for we have a balanced service concept, which means if we are running late we will try and catch up the time, hopefully with a combination of intersection takeoff and higher speeds......its just a concept we have to improve our customer service (would be nice if ATNS and ACSA had a similar concept....but I guess you dont need good service, you have a monopoly dont you?)

I would think an intersection takeoff request would be useful for you guys then you can make the traffic flow to your advantage instead of having a jet wait 5 minutes lined up on the runway waiting for a Dash 8 or a Caravan to move off.

Having witnessed how the traffic flows in London or the US, with many times the volume that we have here, perhaps you could enlighten me why we often end up waiting 5 min between departures (same aircraft type) on a day with not a cloud in the sky, often explained as congestion with Radar. Not trying to pick a fight, but how come they can handle the volumes they do in London and we cant handle the volumes here, is it equipment, training, different separation rules? it cant all be due to poor runway layout.

[borstlap]

Airliners and every operator/pilot working under part 135 or 121 will have to comply with performance compliant aircraft. That means that you are working on a balance field length philosophy, ie at a certain speed (V1) you would have made a decision to either continue the take off or reject. Thus regardless of runway behind you or not, if your aircraft reaches V1 the decision was made already. Now if the length of the runway falls withing the balance field length criteria (to accelerate to V1, reject and stop within the remainder of the field + the stopway, with the most critical engine having failed at V1) it does not matter if there is half the runway behind you or not.
Hope this clarify the issue

[pointer41]

Thanks a lot, all, for the info!

I certainly started thinking a bit wider on the issue than before!
:ok:

[Jelly Doughnut]

Sure you get frustrated with us when we wont let u start, but have you also thought that sometimes we prefer to keep a/c in the bays, otherwise there will just be a traffic jam at the hold and I think (I might be wrong but I dont think so) most pilots would rather sit at the gate than at the hold burning fuel?


Goldfish, not sure about other airlines but at BA we aim to push back on time when possible and absorb any known slot/airport congestion delays during taxying or at a remote holding point. Our "on time performance" look better that way :ok:
Cheers JD

[saywhat]

Goldfish, you say
Having witnessed how the traffic flows in London or the US, with many times the volume that we have here, perhaps you could enlighten me why we often end up waiting 5 min between departures (same aircraft type) on a day with not a cloud in the sky, often explained as congestion with Radar. Not trying to pick a fight, but how come they can handle the volumes they do in London and we cant handle the volumes here, is it equipment, training, different separation rules? it cant all be due to poor runway layout.

SA ATC's undoubtedly control more traffic in SA (JNB) than any other controller anywhere in Europe or the USA. Perhaps not numbers of a/c, but numbers of a/c spoken to simultaneously. Only so many a/c can be controled at any one time for two reasons. Firstly because of time constraints, and secondly to ensure there is not an information overload for the person controlling. The ATC's can only talk to so many a/c at a time. If more sectors could be open, more traffic could be moved. Unfortunately there is a staff shortage in SA, which will not be remedied in the near future. In the UK and USA, there are many ATC's on duty, and therefor they only talk to perhaps 10 a/c in their sector before handing that traffic off to another sector. In SA, ATC's also have to control large volumes of traffic out of Lanseria off 06 simultaneously to a/c out of JNB off 03. Both a/c might be flying south, so just because you don't see the a/c doesn't mean it's not there.

The ATC's are still restricted to 5 mile separation. With the small TMA, and high traffic volumes, this greatly increases their workload. This, I believe is one of the reasons the new STAR's position a/c on downwind rather than base.

I am not an ATC, but I do understand their predicament. I can absolutely 100% vouch for the fact that these professionals do try to to offer as good and expeditious a service as possible.:D :D

[fluffyfan]

I would agree, the individual controllers in my opinion are excellent, its the system and management (ie pay conditions of service etc) that tend to let the system down, maybe more controllers, better pay, but hey lets be frank this is SA..............management (not all sorry its a generalisation) are 50 years behind the first world and its often a case of having the right skin colour and not the right qualifications...........just my opinion

[putt for dough]

thats right fluffly...just your opinion.
we are all entitled to our own opinions!
:ugh: :ugh: :cool: :D :D

[Shrike200]

....management (not all sorry its a generalisation) are 50 years behind the first world........


Nah, it's pretty much all of them! ;)

[saywhat]

If you are early for departure why not phone JHB and see if they can accomodate an earlier landing slot?
Intersection departure are never initiated by ATC in Sa and no intersection departures are allowed if the runway is wet , if it's LVP's or if at night .It's a liability issue.

[Q4NVS]

As far as I understand our SOP's, we can do Intersection Departures whenever the performance figures allow for this (day or night), except with LVP's.

Wet Runway - can even still do Reduced Power/Thrust Take-Off's, but not when it becomes a Contaminated Runway (there is a difference).:=

[Stierado]

There is no way in HELL that JNB are busier than the London airports...

We only fly to Stansted which is a London satelite and some days at rush hour you dont even get a chance to check in on the frequency with all the "break-break calls".

Volume of traffic in the London zones is far greater than JNB.

Controllers everywhere do a fantastic job thou.:ok:

[topo di radar]

ICAO allows for intersection departures. However local state/county regulations or as ICAO refers to them (local ATS Authorities) may impose restrictions there-upon. Reasons for intersection departures are redundant to ATC's as the PIC is ultimately responsible for safety of aircraft and passengers.

In ref to SA ATC's being busier per controller than those in the USA or Europe, somewhat of a naive perspective. SA ATC's have an extremely high standard to which they operate and do indeed work a high level of traffic, but compared to many cetres in the USA, even at county level, they are rather tame when it comes to any one number of aircraft on any frequency at any given time.

The same applies to Europe and most of the Middle East.