Go-Fly: one more minute than most?
Join Date: May 2002
Location: On the edge
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
Hope for the best, but expect the worst
I'm affraid to say it, but ATC also have their part to play in this - e.g. read my contrib on page one of this thread, and perhaps a fuller explanation of that might help:
A B757 is told to line up and wait, whilst an aircraft which just landed vacates.
The B757 is then issued take-off clearance and commences the role - and we're told to line-up & wait in turn behind the departing B757 - which we do.
We start our clocks (based on the start of the B757's role) and we're expecting ( neigh, assuming ) that ATC will be providing the normal two minutes between us and it.
The B757 lifts off pretty much as we apply the brakes to 'wait'.
It then comes as a surprise that at 50" we're issued with our take-off clearance - and at which some might be tempted to blast off down the runway.
We said that "we'd like the full 2 minutes" and to be fair ATC were fine about it - however we got the distinct impression that ATC were trying to 'hustle' us to be on our way (sorry guys, it's just how it seemed) probably because there were loads of other aircraft waiting behind us both to depart and to land.
Of course if ATC are expecting (hoping) that we'll accept an earlier than normal departure - i.e. reduced separation - in order that a landing aircraft can be slotted in behind us then we'd like to know about it PRIOR to lining up on the runway - so saving embarrasment all around, as we sit on the runway waiting for the proper separation, and ATC issue the "Go-Around" instruction to the fella who's hoping to land.
So I think the question I'd like answered is does the two minutes start from when the preceeding aircraft roles or from when it starts generating lift ? - there seems to be some confussion about this. Would any ATC folks choose to enlighten us as to what criteria they use for assessing when the timing for the separation starts on their clocks ?
Ps. A very valid point was made above by outofsynch - in that some here would seemingly be making no allowance for a wake turb encounter when you've just suffered a major mechanical failure of an engine, e.g. in my example above, we'd have looked a right couple of prats if at 50" we'd blasted off down the runway, passed V1, suffered an engine problem, got airbourne at Vr, and then flown into the wake turb of the preceeding aircraft - veritably "One hopes for the best, but expects the worst !"
A B757 is told to line up and wait, whilst an aircraft which just landed vacates.
The B757 is then issued take-off clearance and commences the role - and we're told to line-up & wait in turn behind the departing B757 - which we do.
We start our clocks (based on the start of the B757's role) and we're expecting ( neigh, assuming ) that ATC will be providing the normal two minutes between us and it.
The B757 lifts off pretty much as we apply the brakes to 'wait'.
It then comes as a surprise that at 50" we're issued with our take-off clearance - and at which some might be tempted to blast off down the runway.
We said that "we'd like the full 2 minutes" and to be fair ATC were fine about it - however we got the distinct impression that ATC were trying to 'hustle' us to be on our way (sorry guys, it's just how it seemed) probably because there were loads of other aircraft waiting behind us both to depart and to land.
Of course if ATC are expecting (hoping) that we'll accept an earlier than normal departure - i.e. reduced separation - in order that a landing aircraft can be slotted in behind us then we'd like to know about it PRIOR to lining up on the runway - so saving embarrasment all around, as we sit on the runway waiting for the proper separation, and ATC issue the "Go-Around" instruction to the fella who's hoping to land.
So I think the question I'd like answered is does the two minutes start from when the preceeding aircraft roles or from when it starts generating lift ? - there seems to be some confussion about this. Would any ATC folks choose to enlighten us as to what criteria they use for assessing when the timing for the separation starts on their clocks ?
Ps. A very valid point was made above by outofsynch - in that some here would seemingly be making no allowance for a wake turb encounter when you've just suffered a major mechanical failure of an engine, e.g. in my example above, we'd have looked a right couple of prats if at 50" we'd blasted off down the runway, passed V1, suffered an engine problem, got airbourne at Vr, and then flown into the wake turb of the preceeding aircraft - veritably "One hopes for the best, but expects the worst !"
Last edited by Safety's No Accident; 7th Jun 2002 at 07:47.
On the specifics of this case we would need to hear the tapes.
"We need another minute" might imply a company policy. I might mean we as in the Royal we.
The Go book is clear - standard 2 mins unless intersections are involved.
Looking from a CRM stance:
Take off clearnance is given the Skipper is happy to go.
The FO pipes up "hang on - do we need three minutes behind him?"
-------
At this point the Skipper could say - "no - lets go".
OR
He could say "Tower we need another minute here - now Bob, the book says 3 mins from an intersection behind a heavy. So in this case we only need 2 is my view. Are you happy with that or if you want, lets taxi clear and double check, I don't mind".
-------
Which is the best CRM?
Perhaps thats what happened. We won't ever know.
Its always preferable to ask for extended departure prior to entering the runway. However a million and one reasons can distract you from doing so.
-------
We all know about the injustice of your split second decision being judged by a panel of experts with the benefit of hindsight and time on the subsequent board of enquiry.
We should be mindful of such injustice here.
------
Good and interesting debate though. A most excellent forum this i think.
WWW
"We need another minute" might imply a company policy. I might mean we as in the Royal we.
The Go book is clear - standard 2 mins unless intersections are involved.
Looking from a CRM stance:
Take off clearnance is given the Skipper is happy to go.
The FO pipes up "hang on - do we need three minutes behind him?"
-------
At this point the Skipper could say - "no - lets go".
OR
He could say "Tower we need another minute here - now Bob, the book says 3 mins from an intersection behind a heavy. So in this case we only need 2 is my view. Are you happy with that or if you want, lets taxi clear and double check, I don't mind".
-------
Which is the best CRM?
Perhaps thats what happened. We won't ever know.
Its always preferable to ask for extended departure prior to entering the runway. However a million and one reasons can distract you from doing so.
-------
We all know about the injustice of your split second decision being judged by a panel of experts with the benefit of hindsight and time on the subsequent board of enquiry.
We should be mindful of such injustice here.
------
Good and interesting debate though. A most excellent forum this i think.
WWW
Join Date: Nov 2000
Location: Grobelling through the murk to the sunshine above.
Age: 60
Posts: 562
Likes: 0
Received 0 Likes
on
0 Posts
WWW
You're right, the discussion is over a ONE MINUTE difference. The CAA specifiy Minima, not absolute times, and it wasn't LHR at rush-hour.
Raw Data
The pax would, it's true, be concerned about a go-around, but they would be more concerned about a crash.
Airmanship is about informed judgements, not blind rule-following.
You're right, the discussion is over a ONE MINUTE difference. The CAA specifiy Minima, not absolute times, and it wasn't LHR at rush-hour.
Raw Data
The pax would, it's true, be concerned about a go-around, but they would be more concerned about a crash.
Airmanship is about informed judgements, not blind rule-following.
Join Date: Apr 2001
Location: Southern England
Posts: 20
Likes: 0
Received 0 Likes
on
0 Posts
Firstly, excellent, thought provoking thread. It would appear that the original post was a question of SOP not airmanship and although as has already been mentioned we will never know the "conversation" that led to the response of "er um yes" to the question of Co. policy, maybe a slighty more "diplomatic" answer would have satisfied STOP STOP STOP's curiosity. However, I have a penny'th of thought for the debate and it's this,
We have this excellent tool called CRM at our disposal which we as pilots generally use to good effect, not least by trying to let everybody know what's going on in our "little world" so that they might plan the best course of action, so why do I feel that generally the offer is not reciprocated? Over generalisation it maybe and where I come from they are improving, by chipping away slowly ("track miles please, our number in the queue please, expected time in the hold if available please" etc.) but it always feels like the info is not given willingly. We can all play our part, ("unlikely to make the fisrt R.E.T., may we roll to the end? will 170kts to 5 miles be OK?")
On the vortex question our training Dept. agree with the earlier post that a practicle application of the recommendations is to time from the start of take off roll to your start of take off roll
I'll get my coat.....
We have this excellent tool called CRM at our disposal which we as pilots generally use to good effect, not least by trying to let everybody know what's going on in our "little world" so that they might plan the best course of action, so why do I feel that generally the offer is not reciprocated? Over generalisation it maybe and where I come from they are improving, by chipping away slowly ("track miles please, our number in the queue please, expected time in the hold if available please" etc.) but it always feels like the info is not given willingly. We can all play our part, ("unlikely to make the fisrt R.E.T., may we roll to the end? will 170kts to 5 miles be OK?")
On the vortex question our training Dept. agree with the earlier post that a practicle application of the recommendations is to time from the start of take off roll to your start of take off roll
I'll get my coat.....
Join Date: Mar 2001
Location: UK
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
2 minutes: 120 secs wheels up to wheels up which is why the take off instruction is given maybe 30 secs early. Its usually longer than that though while waiting for preceeding to vacate, etc... hope that helps 
PPRuNe's favourite BABE!!
Join Date: Apr 2001
Location: under the duvet!!!!
Posts: 303
Likes: 0
Received 0 Likes
on
0 Posts
Just to back up what Athene says wake is from nose up till nose touchdown.
We do give take off clearance before the 2 or 3 minutes are up on the basis that generally take off roll takes about 30 seconds.
Any pilot can say he/she wishes an extra minute at any time and no ATC will force them off the runway. It's more than our job is worth, especially if that aircraft then experiences problems due to turbulence!
It would be nice if all pilots said they wish extra time before lining up especially when they can see something is bearing down on finals, but this isnt always the case. I know that from a personnal perspective I would rather send something around on finals than try and "force" any aircraft to take off when the captain isnt happy about doing so.
At the end of the day we all want to go home "fat and happy", not have to spend the rest of the day filling in forms and explaining why an aircraft was put in danger!
We do give take off clearance before the 2 or 3 minutes are up on the basis that generally take off roll takes about 30 seconds.
Any pilot can say he/she wishes an extra minute at any time and no ATC will force them off the runway. It's more than our job is worth, especially if that aircraft then experiences problems due to turbulence!
It would be nice if all pilots said they wish extra time before lining up especially when they can see something is bearing down on finals, but this isnt always the case. I know that from a personnal perspective I would rather send something around on finals than try and "force" any aircraft to take off when the captain isnt happy about doing so.
At the end of the day we all want to go home "fat and happy", not have to spend the rest of the day filling in forms and explaining why an aircraft was put in danger!
Join Date: Dec 2000
Location: World
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
Wake vortexes (?) really begin in earnest when the preceding aircraft rotates for taakeoff. Two minutes is the standard seperation from takeoff end and three if an intersection is involved. These are MINIMUMS. Take as long as you feel you need but do tell ATC before you line up. See CAA and FAA circulars on this subject, also see some videos readily available. It frightens the hell out of me ever since almost getting caught in a 737 wake (in a light a/c) years ago. Ignore it at your peril.
Join Date: Dec 1999
Location: Melbourne VIC AUS
Posts: 116
Likes: 0
Received 0 Likes
on
0 Posts
j_t,
I take it that you're alluding to the Boeing examination of the 737 loss-of-control some years ago. The video emphatically demonstrates the consequences of a hands-off, A/P engaged, slow crossing of the wake of a 727 at altitude. Four cameras are involved, one in the cockpit looking out at the smoke trail, one in a sort of panoramic mode on the top of the fin, and two looking at the instruments.
The fundamental problem is the back-stick applied by the A/P at about 90 deg of bank! From memory, Boeing's thesis is that unless appropriate action is taken, structural failure will occur.
Also from memory, this accident was the root cause of the introduction of real U/A training (sim) for QA and AN, an area not really addressed in heavy RPT prior to that video being circulated (despite, I might add, the multiple requests from Examiners over preceding years). Mind you, QA C&T knew it all!
Gru
I take it that you're alluding to the Boeing examination of the 737 loss-of-control some years ago. The video emphatically demonstrates the consequences of a hands-off, A/P engaged, slow crossing of the wake of a 727 at altitude. Four cameras are involved, one in the cockpit looking out at the smoke trail, one in a sort of panoramic mode on the top of the fin, and two looking at the instruments.
The fundamental problem is the back-stick applied by the A/P at about 90 deg of bank! From memory, Boeing's thesis is that unless appropriate action is taken, structural failure will occur.
Also from memory, this accident was the root cause of the introduction of real U/A training (sim) for QA and AN, an area not really addressed in heavy RPT prior to that video being circulated (despite, I might add, the multiple requests from Examiners over preceding years). Mind you, QA C&T knew it all!
Gru
Moderator
Grusome,
There are several videos I have seen .. the particular one I was referring to (and, while I have copy it is, unfortunately, not at my side at present) showed a similar scenario with the 737 flying behind another aircraft with the 737 in the vortex field. The TP was hand flying as I recall and the interesting bit related to the magnitude of control deflections needed to keep the bird doing the right thing.
On the structural side, the levels of vertical gust which the penetrating aircraft can sustain are quite frightening. There was a very useful RAeS article some time ago which looked at the numbers for a 747 .. interesting.
You refer to the upset concerns and UA training. Both Boeing and Airbus produced similar, very effective, training videos on upset recovery which I think ought to be mandatory viewing for all.
I have some problems with sim training in this area ... the typical structured sim exercise which I have seen tends to be pretty tame and of limited value. If an ad hoc extreme upset is generated there is a concern regarding sim fidelity.
As a result I have tended to train through the structured scenario to justify the box ticking .. and then introduced the ad hoc upsets with appropriate briefing regarding fidelity. The standard recovery recommendations in the Boeing and Airbus videos can be applied in a resulting generic scenario. The result for pilot confidence is palpable ...
There are several videos I have seen .. the particular one I was referring to (and, while I have copy it is, unfortunately, not at my side at present) showed a similar scenario with the 737 flying behind another aircraft with the 737 in the vortex field. The TP was hand flying as I recall and the interesting bit related to the magnitude of control deflections needed to keep the bird doing the right thing.
On the structural side, the levels of vertical gust which the penetrating aircraft can sustain are quite frightening. There was a very useful RAeS article some time ago which looked at the numbers for a 747 .. interesting.
You refer to the upset concerns and UA training. Both Boeing and Airbus produced similar, very effective, training videos on upset recovery which I think ought to be mandatory viewing for all.
I have some problems with sim training in this area ... the typical structured sim exercise which I have seen tends to be pretty tame and of limited value. If an ad hoc extreme upset is generated there is a concern regarding sim fidelity.
As a result I have tended to train through the structured scenario to justify the box ticking .. and then introduced the ad hoc upsets with appropriate briefing regarding fidelity. The standard recovery recommendations in the Boeing and Airbus videos can be applied in a resulting generic scenario. The result for pilot confidence is palpable ...
Stop Stop Stop refers to the wind at the time being 10kts, 60 degrees off, and therefore the vortices should not be a problem. I think that this is a common misconception.
As far as I know, the vortices tend to travel outwards at approx. 6 kts, so this type of wind would be ideal to hold them in the take off path.
As far as I know, the vortices tend to travel outwards at approx. 6 kts, so this type of wind would be ideal to hold them in the take off path.
Moderator
Join Date: May 1998
Location: .
Posts: 250
Likes: 0
Received 0 Likes
on
0 Posts
I've fortunately not experienced (yet) a severe wake turb encounter on takeoff ( though maybe just a tadge of it ).
However, whilst once following a B747 into STN, I had my 737 roll from 25 right bank through to 45 left bank ( all accompanied by the automatic "Bank Angle" warnings ) - all in the space of about 3 seconds !
Similarly following a B737-800 into CPH one night ( indeed I latterly asked ATC if it was a B757 we were behind ) - whilst in a 25 right bank, to intercept the localiser, we were rolled to 40 left bank ( and again plus the "Bank Angle" warnings ) all in the matter of just a few seconds !
Nb. Both of these events occured when the spacing, according to ATC (and our TCAS), was deemed adequate ( read 'Minimum' ) !
And let's not forget that we had the luxury of several thousand feet of air between us and the ground - so let's all be carefull out there !!!
However, whilst once following a B747 into STN, I had my 737 roll from 25 right bank through to 45 left bank ( all accompanied by the automatic "Bank Angle" warnings ) - all in the space of about 3 seconds !
Similarly following a B737-800 into CPH one night ( indeed I latterly asked ATC if it was a B757 we were behind ) - whilst in a 25 right bank, to intercept the localiser, we were rolled to 40 left bank ( and again plus the "Bank Angle" warnings ) all in the matter of just a few seconds !
Nb. Both of these events occured when the spacing, according to ATC (and our TCAS), was deemed adequate ( read 'Minimum' ) !
And let's not forget that we had the luxury of several thousand feet of air between us and the ground - so let's all be carefull out there !!!
Mr WW Welshman: that is an excellent description, which can also mean that there is no room in the cockpit for typical male egos in front of other guys or gals.
By the way, do male Captains try to be any less cautious with female FOs, or is the opposite situation more common?
Crash Dive: several years ago, a Lufthansa A-340 pilot (while waiting for hotel shuttle in San Fran.) told me that once while departing Munich, their very large Airbus suddenly rolled about 20-25 degrees because of a 757 just in front of them. If a 757 can cause an uncommanded roll in a A-340/330, then anything is possible.
By the way, do male Captains try to be any less cautious with female FOs, or is the opposite situation more common?
Crash Dive: several years ago, a Lufthansa A-340 pilot (while waiting for hotel shuttle in San Fran.) told me that once while departing Munich, their very large Airbus suddenly rolled about 20-25 degrees because of a 757 just in front of them. If a 757 can cause an uncommanded roll in a A-340/330, then anything is possible.
Last edited by Ignition Override; 15th Jun 2002 at 07:29.
Join Date: Dec 1999
Location: Melbourne VIC AUS
Posts: 116
Likes: 0
Received 0 Likes
on
0 Posts
j_t,
Sorry, been away.
I understand where you're coming from wrt to sim fidelity. However, I started to give some respect to the math model after an exercise in the AN 146 sim, when, during the B707 Coronial, we took the Coroner on a demo ride, trying to simulate the loss of directional control and consequences that had occurred at ESL.
After making allowances for some of the design features such as Vmca being below the stall speed, we actually got the sim to spin - or at least depart in a like manner to spin entry. Everything, including the visual, was presented in the expected way. As a matter of interest, it consistently took 6000 ft to recover, which met the criteria advanced by another expert witness.
Something to bear in mind when experimenting with big toys!
Also, despite the fears of the sim centre management, we didn't hit the stops or blow any hydraulics. All very interesting.
Cheers
Gru
Sorry, been away.
I understand where you're coming from wrt to sim fidelity. However, I started to give some respect to the math model after an exercise in the AN 146 sim, when, during the B707 Coronial, we took the Coroner on a demo ride, trying to simulate the loss of directional control and consequences that had occurred at ESL.
After making allowances for some of the design features such as Vmca being below the stall speed, we actually got the sim to spin - or at least depart in a like manner to spin entry. Everything, including the visual, was presented in the expected way. As a matter of interest, it consistently took 6000 ft to recover, which met the criteria advanced by another expert witness.
Something to bear in mind when experimenting with big toys!
Also, despite the fears of the sim centre management, we didn't hit the stops or blow any hydraulics. All very interesting.
Cheers
Gru
