Call V1 3 to 5kts prior

[TQ]

What's up with some of these US airlines that have procedures where you call V1, 3 to 5kts prior ?
What do you think ?

[Pugilistic Animus]

nothing's up when your fence height is ZEEERO

No clue--ssg must be their DFO--or CP:}

[411A]

Some don't have a call at V1 at all....only 'minus five' and 'rotate.':}

[BANANASBANANAS]

It's all to do with the fact that V1 is a maximum 'brakes on' speed if you decide to carry out an RTO. If the decision process starts at V1 and the decision is then made to RTO, the brakes on speed would be above V1.

Boeing state that the decision to carry out an RTO must be made prior to V1 and the first action (thrust levers closed, brakes on) must be carried out at, or prior to, V1.

Different carriers cater for this in different ways. Some call V1 slightly early, others will always use the WET V1 figure, even on a bare/dry runway. Ours just emphasises that the decision to RTO has to be made prior to V1 and that the RTO must be commenced by V1.

As an airmanship point it is always important to know what your limiting performance criteria is. Eg, if you are climb limited you will have some spare stopping performance in hand but if you are field length limited then a V1 RTO will leave you in very close proximity to the wrong end of the runway.

[shazzmo]

The logic is that if you start saying "v1" 3 -5 seconds prior to hitting the speed, the pilot flying knows that you have reached V1 when you finish saying "v1". If you start to call v1 once you reach v1, by the time you finish saying it you are past it and therefore no longer in a position to make a "go-no go" decision.

Anyhow, that's the idea.

[Pugilistic Animus]

Different carriers cater for this in different ways. Some call V1 slightly early, others will always use the WET V1 figure, even on a bare/dry runway. Ours just emphasises that the decision to RTO has to be made prior to V1 and that the RTO must be commenced by V1.



Read some of Old Smokey's Posts and You'll know that's bad:=

[Pugilistic Animus]

Calling V1 at V1 has more to do with pilot incapacitation then stopping---the PF should reference his his/her own ASI

[SNS3Guppy]

I dunno about others, but we say "Vee One" at V1, 'Vee Rrrr, Rotate to XXX degrees" at VR, and call out V2 as it passes. Target climb V2+10.

No need to call anything prior, and it all happens soon enough.

[Pugilistic Animus]

never thought it neccesary to call V are and Vee two---some SOPs require it though

[stilton]

Calling V1 at-5 kts is standard practice with my airline.

As already stated, to ensure that a reject is not started above V1.

By the time you have said it it's too late to stop (unless you are 'ssg') :eek:

[Denti]

Quite a few aircraft in our fleet call V1 on their own (V1-autocall), only call the PM has to do in that case is "Rotate". If we do not have automatic V1 calls we have to do it ourselves. No response on either call is required, but at V1 the CPT has to remove his hands from the thrust levers, and on "Rotate" of course rotation has to be started.

Personally i was trained to start saying V1 3kts earlier, however that is not SOP in my current company so i just do what they require.

[Bubi352]

If you took off from LaGuardia you would understand this procedure. Runway is short and a nice pool of water is waiting for you at the end. Totally makes sense.

Last time I plugged in the numbers in the MCDU, we had only 6 feet of accelerated stop distance remaining if we decided to abort exactly at V1. Do I want to abort in the case right at V1? I don't think so. Remember this is based on perfect conditions.

[SNS3Guppy]

never thought it neccesary to call V are and Vee two---some SOPs require it though


We've got several calls that I'm not sure are necessary, including the V2 call. However, at Vr, we not only call it out, but also add "Rotate to XXX degrees," as part of the standard callout. It's printed on the TOLD card anyway, as our target engine-out pitch attitude, but the SOP is to call it out verbally, anyway.

I'm one of those who responds with a thank you or precedes with a please. I don't see that as extraneous or out of line, but I've sure met a few who had a fit because those "extra words" were apparently just too much to handle. When I say "Set reduced thrust," and the FE responds "reduced thrust set," I reply "thank you." It's not in our standard callouts. I did it in the sim and got loudly berated by the check airman. That individual felt that any extra syllables might bring down the four horses of the apocalypse and perhaps a small infestation of rodents. I don't think common courtesy is out of line.

I sat down with an old salt FE one day who said "You can call me anything you like but I expect a please and thank you." I respect that, and try to give it anyway. Even if it's an extra word.

[Ttree Ttrimmer]

As Bananasx2 states the problem comes from being field limited. If you are and you call V1 early do, you enough runway to accelerate to Vr and clear the screen height in the event of an engine failure between your artificially reduced V1 and Vr? Possibly not. I think the Boeing verbiage is that a stop must be initiated by V1 but the mechanics of it allow for a certain amount of 'thinking time'. There is a value laid down but I can't lay my hands on it currently and it is therefore understood that the aircraft may accelerate beyond V1 by a certain margin before the stop is initiated. I have seen written in several manuals that a stop initiated at V1 on a limiting runway may result in the aircraft not coming to rest on the paved surface. This is due to the calculations being made for a perfect aircraft, on the perfect day, by the perfect pilot and we all know there is no such thing as the perfect aircraft or the perfect day!

[Bubi352]

Yes, with the current price of fuel we are using Flex takeoffs. Obviously, if anything seem out of place we go to TOGA. No questions asked.

It is not the first time I takeoff from short runways and a pool of water (aka LGA) and every time the software gives you performance numbers right on the edge for the most optimum Flex temperature. 2 weeks ago, I remember the accelerate stop distance remaining being 1 feet! You can imagine how our briefing went...

[flyr767]

It's to cover the time it takes to remove your hand from the throttles to the yoke.

[White Knight]

Well on the 'Bus the autocall is a couple of knots or so before V1, and it's NOTHING to do with incapacitation.... It's just that if you are length limited it stops you from over running if you start the abort at V1 - it takes a couple of seconds to even DECIDE to stop - by then you're V1 PLUS X kts and you're possibly stuffed...

[kme]

I think 2 seconds of reaction time should be allowed for in the v1 calculation. Dont know where I got it from but it came up when I read the discussion.

Not much but at least something

[Intruder]

It's all to do with the fact that V1 is a maximum 'brakes on' speed if you decide to carry out an RTO. If the decision process starts at V1 and the decision is then made to RTO, the brakes on speed would be above V1.

Boeing state that the decision to carry out an RTO must be made prior to V1 and the first action (thrust levers closed, brakes on) must be carried out at, or prior to, V1.
Please cite a reference for "Boeing," since your claim is contrary to the governing FAA regulation. Note that the FAR already mandates that V1 is corrected for realistic reaction times, determined via flight testing:
§ 25.107 Takeoff speeds.
(a) V1must be established in relation to VEFas follows:
(1) VEFis the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VMCG determined under §25.149(e).
(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1may not be less than VEFplus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests.

For those who choose to call V1 3-5 knots or 3-5 seconds (per shazzmo) prior to actual V1, you risk that in the limiting case of accelerate and fly with an engine failure at LESS THAN V1 but AFTER the call, you will not get off the ground in time because of the additional acceleration time without the engine. If you KNOW what the limiting factor is in your specific circumstances, you MIGHT want to take that risk. If you do not KNOW the limiting factor for THIS runway/weather/TOGW case, you may want to reconsider...

[Analyser]

On the Boeing 737's with the AUTO V1 callout, the call is made exactly two knots before V1.


kme...thats probably where you got the figure.

[BANANASBANANAS]

Boeing Flight Crew Training manual as issued to our Airline.

As the airspeed approaches V1 during a balanced eld length takeoff,
the effort required to stop can approach the airplane maximum stopping
capability. Therefore, the decision to stop must be made before V1.

[PantLoad]

The issue of V1 is a touchy one. Many operators have different policies, based on their individual experiences.

One thing to note, depending on when the aircraft was certified, the V1 issue is different. As stated above, we're supposed to have something like two seconds reaction time...and still be able to get it stopped. But, this is based ont the new certification standards (both JAA and FAA).

I'm not sure about the NG737, but the older ones were certified under the old system...whereas, you really need to be transitioning to the 'stopping mode' at (or before) V1. Under the old certification standards, any speed above V1 (in an abort scenario) is not good (e.g. two seconds after reaching V1).

The Bus, on the other hand, even though it was produced under the old set of standards, meets the new criteria. That is, you can actually 'initiate' the abort at V1...and still have runway to get it stopped. "Initiate" means, you recognize the need to reject the takeoff (at V1), and promptly do the drill. Again, under the old certification standards, you don't have this.....under the old standards, you really need to have the stopping process going for you as you reach V1.

I can't remember exactly when this certification change occurred, but I'm thinking it was around the early nineties. Again, not sure about the 737NG, as it may still be certified under the original 737 certification rules.

From a practical standpoint, we're talking about only a couple of knots. Sure, as stated above, screen height is affected to some degree, but not significantly...i.e. not nearly the difference of 35 feet vs. 15 feet (dry vs. wet).

Of course, this is all based upon a 'balanced field length'. Some might define 'balanced field length' as "You're dead if you stop; you're dead if you go!" Again, in practice, if bad things happen near V1, you need to be "go minded" as Boeing and Airbus (both) recommend. Who defines 'near V1' is why we have stripes on our shoulders.

Fly safe,


Pantload

[ARINC]

Boeing Go /No Go videos

Part 1

http://www.youtube.com/watch?v=raCnJgDnijw

Part 2

http://www.youtube.com/watch?v=WhVVAI8drVo&feature=related


3 Seconds decision time....?

Accelerate stop go distance remaining of less than 6ft :\....that could prove interesting

[TQ]

Taking the liberty of knocking of 3-5 kts from your performance calculation, to my opinion defeats the whole purpose of calculation.
If you move your V1, it will help you to stop, but it won't help you if you continue your takeoff with an engine failure that could have happened between that -5kts and V1. So what do you do when you are obstacle limited but have enough runway in front of you. Do you call V1 after V1 ?
I'd rather get off the runway while on the ground, than hit the building while in the air.
These procedures go against the whole performance calculation that was designed by the builders engineers, and give the freedom to airlines and pilots to interpret a given situation to their own standard.
Where do you draw the line ?

[FE Hoppy]

V1 is scheduled after Vef. The time gap depends on the certification standard. The gap is already in the calculation so you need to make the first action to stop at or before V1.

If you make the decision to go before V1 you will compromise your screen height.

If you make the first action to stop after V1 you will compromise your stopping distance.

This is for the engine failure case only, and when at your max take off weight balanced field length limited.

Other cases will be different.

It is possible to include stopping distance allowance to hedge the stopping case and of course line up allowance must be used where necessary.

It's just not black and white.

[RYR-738-JOCKEY]

I totally agree with TQ.
If you choose to tweak the numbers for a balanced T/O, then you better think about the other end of that equation too. :hmm:
If you continue with an EF at V1-5, then you need abit more than your ASD to get to your 15' screenheight at rwy end.

[PantLoad]

Well, you are not knocking off 3 to 5 knots from your calculations. You're simply calling V1 in a timely manner to ensure that you do not initiate the rejected takeoff at a speed above V1. In point of fact, you're respecting V1, not changing, modifying, etc.

Again, the issue is dependent on when the aircraft was certified. Under the old certification, you really don't want to allow the aircraft to attain a speed above V1 before the stopping actions are initiated. If you call V1 at V1...have an engine failure at V1...and you try to stop (assuming you're field-length limited), you've got a problem....because, before you know it, you're going V1 plus a couple...then, you initiate the rejected takeoff drill....BIG PROBLEMS!!!!!

We're talking only a second or two in time.....makes a big difference for 'stopping'...not much difference in 'going'. According to engineering data, even if you lose an engine at, say, V1 minus 2 or V1 minus 3...and continue the takeoff...you'll find the reduction in screen height is reduced minimally...like maybe ten or so feet. (Still above the 15 foot wet-runway figure)

But, if you lose one at V1 minus 2, and you try to stop...you'd better hope you do things very quickly...you'd better hope the brakes are in good shape (not worn to just above minimum limits)...you'd better hope the runway surface at the other end of the runway is not contaminated...or full of rubber or other crap....in other words....if you reject at V1 (and you're field-length limited), things have to be perfect for you to stop before the end of the runway.

In contrast, losing one at V1 minus 2 and continuing the takeoff will have minimal consequences. This is why the manufacturers say, as you approach V1, you need to be more 'go minded' and less 'stop minded'.


PantLoad

[cattleflyer]

Bubi...that's what I thought. No doubt using full power, would give you more room at V1 to make a decision, which has been the main argument against flex for some time.

[SNS3Guppy]

which has been the main argument against flex for some time.


Not "the" arguement. Just your argument. Of course, it's a lone argument and you keep getting banned, only to pop up under a different rock each time...and it's a weak argument with no foundation. Doubtless you'll keep making it, though.

You're on the ignore list as of...now.

[Mad (Flt) Scientist]

Re all those discussing "reaction times". You emphatically do not have two seconds reaction time at V1.

25.107(a)(2) requires that V1 be not less than Vef (engine failure) plus pilot reaction time.

Therefore the reaction is to the engine failure - not to the point at which V1 is attained. And the time is not necessarily two seconds either - it's however long the test pilots took during certification testing. (AC25-7A directs that the time used for calcs be not less than one second).

The notion of a two second reaction time is likely coming from a reading of 25.109, which states ...

§ 25.109 Accelerate-stop distance.
(a) The accelerate-stop distance on a dry runway is the greater of the following distances:

(1) The sum of the distances necessary to—

(i) Accelerate the airplane from a standing start with all engines operating to VEFfor takeoff from a dry runway;

(ii) Allow the airplane to accelerate from VEF to the highest speed reached during the rejected takeoff, assuming the critical engine fails at VEFand the pilot takes the first action to reject the takeoff at the V1for takeoff from a dry runway; and

(iii) Come to a full stop on a dry runway from the speed reached as prescribed in paragraph (a)(1)(ii) of this section; plus

(iv) A distance equivalent to 2 seconds at the V1for takeoff from a dry runway.

Yet a review of AC25-7A reveals that it states quite categorically that the 2 second distance allowance is not a "pilot reaction" time and must not be considered as extending the decision-making and reacting process past V1 ...

.... Thus it can be seen that V1 is not only intended to be at the end of the decision process, but it also includes the time it takes for the pilot to perform the first action to stop the airplane. The purpose of the time delays is to allow sufficient time (and distance) for a pilot, in actual operations, to accomplish the procedures for stopping the airplane. The time delays are not intended to allow extra time for making a decision to stop as the airplane passes through V1. ...

(Section 11(c)(3) of AC25-7A chg1, page 80-6, for those who wish to see it in its full context)

So AT V1 you MUST have taken the first action to stop the plane (if you're going to abort) and you have two further seconds to complete ALL the actions required to stop the plane if you are to achieve the OEM's calculated stopping performance. Any slower timings and you are not guaranteed to remain on pavement.

=====

Given all that, it makes perfect sense for the V1 call-out to begin before V1 - for it to be useful, the fact that V1 has been passed must be processed by the PF at the point of V1, if not before. If the PNF starts to call "Vee-one" as V1 is attained then by the time he has finished, and the PF has processed the info - perhaps 0.5 seconds for reasonable human reaction times - it's already too late.

[Mad (Flt) Scientist]

@PantLoad:
you'd better hope the brakes are in good shape (not worn to just above minimum limits)...

While a perfectly respectable hope - any margin is worth having in a max energy RTO - the numbers are, at least in theory, good for "fully worn" brakes, and must be demonstrated with 90% worn brakes in the max KE case.

[PantLoad]

Mad Flt Scientist:


With regard to brake condition at the beginning of the RTO, is the old certification standard with worn brakes? I have to research this, because I thought the old standard was with new brakes...the new standard is with (I can't remember)...either 50% or worn-to-limits brakes.

Please correct me...I'm not sure...but, I'm thinking that was changed, too, along with the V1 standard. (You usually have a pretty good handle on details like this.)


PantLoad

[Mad (Flt) Scientist]

Sorry, I missed that your whole post had an "old cert rules" qualifier in the second para.

The new rules require worn-to-limit brakes (or a correction to that state). As to the old regs ... wait one.

OK, the max KE demo with 90% worn brakes came in with Amdt 25-92 in 1998. Prior to that the Accel-Stop para (25.109) had NO max KE requirement. (Though other paras may have applied, at least in part - 25.1301 "performs its intended function" comes immediately to mind as one candidate para)

The fully worn requirement is actually 25.101(i) and also came in with Amdt 25-92. Again, one could have argued about other regs. But there's nothing explicit.

[PantLoad]

Yep, you came through again!!!! Thanks. You're usually very good for posting the details.

It was in the early nineties, as I recall, a major carrier in the U.S. had an RTO accident...short/wet runway, non-standard grooving, a lot of rubber at the end...anyway, while they hung the captain, a lot of procedures changed. One new procedure that was implemented was that of a reduced V1 when on wet runways. Of course, another change in the SOPs was that of calling V1 five knots early...stressing the importance of (in the case of rejecting the takeoff) beginning the RTO procedure no later than V1 (in essence, not allowing the aircraft to accelerate above V1).

I remember the political nonsense (feel free to substitute another eight-letter word), as I was at the seminar held by Boeing that addressed this particular accident.

At the end of the seminar, there was a Q & A session...a couple of Boeing test pilots and engineers were running this thing...and, I had a bunch of questions...several questions they didn't like hearing, much less answering. My relationship with my company (my job) and with Boeing were never the same after that. In fact, my boss explicitly told me in front of everyone to sit down and shut up.

But, while the captain of the aircraft involved in the accident certainly had some blame coming to him, he was the victim of a stacked deck of cards against him. I had to make that point to Boeing. (Of course, they already knew this...I just wanted them to know that we all knew it, too!)

The accident was a fatal one...the captain has to live with this for the rest of his life. But, as a result, several SOPs have changed; runways are now getting standard grooving; runways are being steam cleaned more often. And, hopefully, things like this will not happen again.

Thank you, again, for this post and all your other posts which are quite informative.


Fly safe,

PantLoad

[adverse-bump]

In flight testing, the v1 one has a 2 sec decision, and a 2 sec reaction built into it. so why would you take an extra 5 sec off? why not go with the flight manual?

[Bubi352]

CattleFlyer - All I said is if something doesn't feel right during a Flex takeoff you can go to TOGA at anytime. Additional thrust is available and I will use it if necessary. I have not read your previous posts but you seem to point out that Flex takeoff are not safe - wrong. Read more about balance fields. You will have a better understanding of the concept of V1.

[Mad (Flt) Scientist]

In flight testing, the v1 one has a 2 sec decision, and a 2 sec reaction built into it. so why would you take an extra 5 sec off? why not go with the flight manual?

Flight testing has no such thing, nor do the certification rules. And, as explained above, the flight manual is predicated on not just recognition but reaction having started at V1. Which means if AT V1 is when you start the "V1 process", you're already behind the aircraft.

[Clandestino]

It's very simple.

Pilots with zero reaction time, able to pronounce "vee-one" in zero seconds are right to call V1 at the time they see their ASI pass through one.

Others, who somehow fail to meet the criteria have to cater for it. Personally I call "GO!" 3kt before V1, per SOP.

[PK-KAR]

Why would anyone with 200 pasengers in the back, intentialy choose to risk thier lives by flying right to the edge of being able to reject a flight safely?
Do I see v9.0 here?

Overunning into the wall, going off into the bay, off the cliff or into some houses doesn't seem like a fair trade off to save on some fuel.
Save on some fuel? Do I read that right? You are talking about flex/derate take offs right? Last time I checked, fuel burn wasn't the considered factor for flex/derate take offs.

[boofhead]

I thought I had heard all the calls that airlines make, but calling the target attitude during the rotate call is surely one of the most ridiculous ones out there. The attitude changes that much to have to have a reminder at a time when the pilots should be concentrating on their job of flying the airplane? For the 2 minutes or so a modern pilot actually flies, that is? And will the PNF be smart enough to adjust the figure for an engine failure? And what about the flight director, which has been programmed to give the best attitude soon after lift off anyway? Is the PF so ignorant he even needs this call? If he does not know what attitude to rotate to what is he doing in the seat?
Talk about flying with your tongue! What would you do if there was a genuine need to make a callout of a malfunction or error? The pilot is already expecting the garbage call, and will tune it out. If the PNF is wrapped up in this call, will she see anything going wrong elsewhere?
Keep the calls to a minimum. Only call when there is a non-standard situation, so the call will be heard and listened to. Extraneous calls of the bleeding obvious reduce safety by being a distraction and reducing situational awareness.
I surely wish the airlines would stop mucking about with the manufacturers' operational procedures.

[eight16kreug]

Old Airbus callouts: Flaps One. Speed Check, flaps one, selected. Indicating.

Current callouts. Flaps one. Speed Check, Flaps one.

I think the trend is towards less callouts.

[Basil]

I surely wish the airlines would stop mucking about with the manufacturers' operational procedures.
You're certainly preaching to the converted with me :ok:
Re verbosity; flew for an outfit which Called: "Set thrust 1.nn EPR!"
I always felt that I should be looking outside at that moment rather than glancing at the card or the EPR bugs.

[UL975]

I may be wrong, (have been in the past:ok:) but I thought that very simply put.....


FAA performance V1 has no fudge factor bult in.

JAA adds a 2sec fudge factor to the V1 speed.


So the operators calling V1 before V1 are probably FAA airlines adding their own fudge factor.

[safetypee]

See
UK AIC information on RTO. (www.nats-uk.ead-it.com/aip/current/aic/pink/EG_Circ_2006_P_024_en.pdf) This is based on JAR/CS 25 certification requirements which have (as far as possible) been harmonized with FAR.

The decision speed (V1) is the highest speed by which the pilot should have made the mental decision to reject the take-off in the event of a relevant failure.

A recognition period (distance) is included in the certificated data – Vef is prior to V1; crews need not be concerned with the technicalities, just respect V1.
A period (distance) after V1 is provided in the calculations to enable completion of the RTO drills, again crews need not be concerned with these values; perhaps more so with the accuracy of the speed setting and total distance required to stop.

It might be of greater importance to understand what failure or condition determines the need for a RTO as opposed to time periods, and then preparedness for timely and correct action if the decision is to stop, e.g. apply maximum braking. Beware the human limitation from time dilation in judgments made in stressful conditions.
Does anyone have procedures that require manual braking even if auto brake is selected – mitigates any error in setting autobrake?

Note new UK AIS web site. (www.nats-uk.ead-it.com/public/index.php.html)

Also, see ‘accelerate-stop time delays’ AC 25-7A Flight test guide for certification of transport category airplanes. (www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/MainFrame?OpenFrameset) Chapt 2, a good diagram on page 80/9.

[mutt]

AFAIK, there are 5 versions of FAR25.109.... so a blanket statement regarding reaction times and engine failure point, may not apply to YOUR specific aircraft.

For example, the B777 has the VEF 1 second prior to V1, with continued acceleration until complete stopping congfiguration is achieved.

Mutt

[oldfella]

I may be out of date on my definitions and understanding so apologies if I am wrong. I thought that a rejected take-off before V1 was guaranteed to stop within the ASDA i.e. TORA and Stopway, not guaranteed to stop on the runway, however, with no stopway, e.g.Gibraltar, ASDA = TORA and, in theory, you would not get your feet wet. A lot of assumptions are made that you will stop on the runway.

[Pugilistic Animus]

I'm one of those who responds with a thank you or precedes with a please. I don't see that as extraneous or out of line, but I've sure met a few who had a fit because those "extra words" were apparently just too much to handle.

Guppy,

Yeah, today people in aviation get excited over immaterial things and yet blissfully ignore very important operational concepts if they're not explicitly written as sops---the answer--- longer more confusing procedures---to create higher risk of RWY incursions:\



OldFella,

the geometric definitions haven't changed, just the perfermence requirements along the length of the defined 'sectors', so you're absolutely correct:)

Thanks,

PA

[john_tullamarine]

Post A/L 42 aircraft are in a more comfortable situation .. pre amendment aircraft represent a VERY critical accel-stop in limiting conditions.

[Pugilistic Animus]

John T,

How would you characterize the accelerate-GO?--in a limiting situations---but I guess this may have biased one toward non-BF calculations and where possible a lower V1?

PA

[john_tullamarine]

(a) considerations of BFL, unbalancing, overspeed schedules, etc., are all made before the takeoff as part of the performance assessment. This is done either in the preparation of RTOW tables/charts by the ops engineering folk, or by the pilot in those operations which impose that task on the crew.

(b) if the takeoff is accel-stop-limited then, in the GO situation, if the sums have been done acceptably, aircraft and pilot performance and weather are reasonably similar to the certification expectations ... then it should be a matter of just flying the aircraft through the exercise.

(c) if the riders attached to (b) don't apply then, just perhaps, the crew and operator have their collective necks on the line ?

[Pugilistic Animus]

a) considerations of BFL, unbalancing, overspeed schedules, etc., are all made before the takeoff as part of the performance assessment. This is done either in the preparation of RTOW tables/charts by the ops engineering folk, or by the pilot in those operations which impose that task on the crew.




As usual JT ---wise and knowledgeable words--- but I was referering to the engineering side--not the end user---i.e if on an earlier type of older certification do you tend to unbalance according to the limiting cert scenario in the RTOW assumptions? is it such that unbalancing occurs mainly in the ASD--but leave the BF for the GO--just wondering how a pro would handle it?---I have looked at the preammendment requirements, but would like to know how such things affect the performance calculations:)

PA

[PantLoad]

Mutt is correct.....it depends on the standards under which the aircraft was certified. His B-777 was, I believe, certified, after certification standards underwent major changes (subtle on the surface, but quite significant).

FAA/JAA and manufacturers have been for years aware of the shortcomings of this stop/go dilemma. The accident I cited in my above post brought to light the issue of inadequate certification standards in this reagard.

Of course, your company's SOP takes priority over everything...as this is one of the predicates upon which the airline operating certificate is granted. (I know, this is a controversial statement.... But, you need to follow your SOP. If you find a problem with anything in your company's SOP, you should bring this to the attention of management.)

And, as always, be careful out there....



PantLoad

[Pugilistic Animus]

PF: SET POWER
PNF:SETTING POWER

PF: AIRSPEED ALIVE
PNF:CROSSCHECK
PNF: CONFIRMED POWER SET 1.06epr UNITS

PF: 60 KNOTS
PNF: CHECK
PF: 80 KNOTS--ENGINES STABILIZED
PNF: CHECK --ENGINES STABILIZED
PF: ONE HUNDRED KNOTS
PNF: CHECK ONE HUNDRED KNOTS
PNF: V1 FIVE TO GO:}
PF: CHECK

PF:VEE ONE

PNF: CHECK VEE ONE
PNF: VEE ARE ---ROTATE:}

PNF: VEE TWO:}


PF: CLEAR OF GROUND POSITIVE RATE GEAR UP

PNF: GEAR UP--AND LOCKED
PF: CROSS CHECKED

PNF: APRROACHING ACCELERATION ALTITUDE

PF: SET CLIMB POWER

PNF: CLIMB POWER SET

PF: ACCELLERATING --FLAPS SCHEDULE

PNF: FLAPS UP

PF: CHECK FLAPS UP:}

ummm....where the hell are we going:}:}:}????

Sorry, couldn't resist---everyone gets the joke:}

[mutt]

Look dude, if you are going to keep coming in here using different user names... please learn to spell OBSTACLES correctly, otherwise you are just making things too easy!!!!!!!

Mutt

[john_tullamarine]

but I was referering to the engineering side--not the end user

If I read your question correctly ...

(a) the takeoff calcs are for one set of runway data ... you can't make one bit BFL and another bit unbalanced, etc.

(b) nothing secret about the process .. for those aircraft whose AFM permits unbalancing, one just iterates the calculation with different levels of unbalancing until the RTOW for that given data set is maximised.

(c) this is constrained a bit if the output is graphical but, for the normal tabulated RTOW tables, it is a doddle and each point can be optimised without consideration of others .. at the end of the day the pilot needs the speed schedule and the unbalancing extent is buried within this output.

(d) there is no reason why the data cannot tell you the extent of unbalancing but that is not normally done

If I have missed your point, do try again and I shall endeavour to be a more diligent reader.



Mutt .. that's a tad cruel ....

[Mach E Avelli]

With reference to the Gear Up call I once had to endure the response 'selected, 3 reds' followed by 'gear is up, lights out'.
No one ever told me what to do between then and until after final clean-up if there were only 2 reds. Hold the checks, maybe?
At the risk of thread drift, other useless classics include during takeoff 'temps and pressures checked' , 'on finals, no flags' and in response to the 500ft rad alt call 'for the threshold'.

[Brian Abraham]

Mutt .. that's a tad cruel
I thought mutt showed considerable restraint, a measure of delicacy and tact. Quite unlike some. :E

[TheChitterneFlyer]

V1 or V1 minus 3-5, what's the difference... you're still likely to be eating dirt if you stop. Plus an interview that doesn't include tea and biscuits... hat on!

TCF

[Pugilistic Animus]

JT---the prior post was helpful in removing some confusion I had---although, and I blame my own phrasing,---but what I'm really getting at id

when you do the RTOW charts---is it's a good decision to use --let's say for example---I'm on an ASD RWY for a given set of condition, so I use unbalanced data iteration for that limiting case---for another set of conditions my ASD is adequate, but I'm climb limited so--I use the BF UBF data[whichever will allow the higher weight---but the end user is unaware--or am I jus' makin' up stuff?
but does 'mixing the two' on a RTOW--allow higher weights if the RTOW--is produced from different sets of data--of course the end user will have no clue;)

Thanks,
PA

[mutt]

PA, its called optimized v-speeds and is available from all your favourite manufacturers.................

you're still likely to be eating dirt if you stop not always true... but hey this is pprune!!!!

Mutt

[Pugilistic Animus]

thank you Mutt,

I know that optimized speeds are available, but what if you have an 'older type' 737-200, 727, DC-9 etc.... that was granted certification under older rules---is such data available?

or do you/could you do it on a ad hoc basis--- optimize your V speeds? if you have BFL and UBFL data or is it too cumbersome or do any other caveats apply?

PA

edited to say---that I was thinking more of the older types in my original question---but I now know how to at least ask the question:}

[Jaxon]

3 to 5 knots before V1 is the only way for the two humans to react in accordance with the actions/decisions required at or before V1.

[john_tullamarine]

I'm on an ASD RWY for a given set of condition

Not quite sure what you mean here .. unless, perhaps ASD-limiting runway.

It still appears that you are trying to mix distances in the one calculation .. (mind you, it is late at night and I might be just a tad thick and not understanding where you are coming from ..)

For a given calculation (ie runway, OAT, W/V etc ...) if you are using BFL then you just calculate the various cases and the worst ( ie lowest weight) gives you the answer

If you have the (AFM) ability to unbalance the calculations (some AFMs don't give you the option so it is BFL whether you like it or not)

(a) you don't necessarily use ALL the TOD/TOR/ASD for the various cases .. some AFMs give you opportunity to calculate each separately (which means you can) while others (most) have a combined method of calculation which restricts the opportunity for playing around with the numbers

(b) by iterating the calculation (doing it repeatedly with variations in the input parameters) you can end up with the best weight for the day. Generally only one of the cases will determined the critical calculation


could you do it on a ad hoc basis

If, by ad hoc, you are looking at the pilot doing the calculations and optimising the RTOW, then that would depend on what data he/she has available (whether simplified ops manual stuff or detailed AFM) ... refer back to the earlier comments if you have suitable data.

Main thing is .. generally it is too long winded for the line pilot to run a full AFM calculation (not to mention plain tedious and boring) .. however, regardless of whether the calculation is AFM, ops manual simplified data .. or just looking up some RTOW tables ... the degree of unbalance (which is the same as saying V1/VR ratio) applies to all the calculation cases simultaneously .. ie you can't have different degrees of unbalance for the TODR, TORR, and ASDR by running the calcs for varying V1/VR as the calculation case varies .. would give inconsistent answers.

Or am I still missing the point which is of concern to you ?

[Callsign Kilo]

SOP with my airline - V1 call must be completed by V1. Something to do with Boeing studies into average reaction times when a decision to abort the take off at or just before V1 is made.

[Pugilistic Animus]

Professor Tullamarine, Sir---I think I need a little time to properly formulate my question---I don't think I know what I'm trying to ask myself---but something's confusing me:\---I'm trying to think how to properly formulate my query--with Mutt's reminding me of optimizing V-speeds---I THINK --that I mean to ask--from the engineer's view--not the line pilot's---how do do your own optimal analysis-?-when you have BF and UBF data---but no optimum data?


Thanks again,
PA

edited to write, I did indeed , mean ASD-limited:O----I think that Ssg in his various permutations, diminished my intelligence a bit---a made me a little fet:}

[TheChitterneFlyer]

Anyone would think that Take-Off Performance is an exact science; which at best is an averaged set of numbers that will give some guidance as to where you 'might' actually stop if it all goes pear-shaped.

Hey, three to five knots is probably a good range that an 'averaged fleet' might achieve; within a couple of hundred yards of that vital bit of runway that allegedly guarantees you stopping within the remaining 'stopway'... hence, eating dirt! Given that you and I have the same aeroplane, both of them will differ by an incalculable amount; therefore, does it really matter? During my Performance Course, many many years ago, I recall that a couple of seconds or so were factored into the numbers to allow for pilot recognition/response time of an engine failure... why beat yourself around the head with trying to get the words out in time when the response time has allready been factored-in? So what, if you're a couple of milli-seconds overdue in making the call; don't anticipate it... just do it! There will, in all probability, be a difference of a couple of knots between the ASIs anyway! Perfectionism is one thing... but let's not take it too far!

TCF

[Pugilistic Animus]

TheChitterneFlyer

Jet piloting IS AN EXACT SCIENCE---WE ---sometimes get it--- Tight, Tight---and maybe right down to the wire---hence the big bucks:}

PA

[Pugilistic Animus]

Wow, everyone seems to be an expert in error analysis----jus' compute[numerically, graphically, or functionally]--the second derivative of the relevant function---in order to find the ZERO SLOPE tangent to the curve and find the min and max tolerance values of your funtions---if you have an equation handy take the second derivative and set that equal to zero---do that for many hundreds of functions and report that data as---xxx0 units +/-.0023units--then submit that analysis to Boeing or Airbus--so that Mad Flight Scientist can then build a flight test schedule with their test pilots--once airworthiness certification of the ship and the AFM is done place---submit that data to performance experts like, Mutt, John Tullamarine, or Old Smokey--where they can then use the data to meet the air carrier requirements--so that the plane can be used to make money---You might require some rest afterward:}--but then YOU can do whatever the HELL you like at V1---until then:=

Get it, Got it, Good,


Those Slick Engineers!!!:E
PA

[Pugilistic Animus]

IF BY VI THE THRUST LEVERS [LET'S ASSUME THAT THIS IS THE FIRST AFM REQUIRED STOPPING ACTION--UUM KAY]---ARE NOT {{RETARDED}} THEN FOR :mad: SAKE YOU GO! GO! GO!

[TheChitterneFlyer]

Pugilistic Animus; been there; got the T-Shirt but the 'exact science' bit is a tad over the top.

I too have seen the very end of many runways; the fact still remains that at MAUW and a couple of knots prior to V1 and you call 'STOP'... you're into the stopway; no argument there I trust!

By the way, where do the 'big bucks' appear in the equation?

[Pugilistic Animus]

That's why those foolish Inginears--Dem Bums!--include the stopway in the EMDA or ASDA sometimes the EMDA is the ASDA--but no te preocupes--they'll pay for the bogies--don't pay for the bogies with your life---the NTOFP already had reductions in it do put more out on the other side ---tight--tight:\

re: pay don't you see the lil 'crackle tooth' smiley:}

[john_tullamarine]

when you have BF and UBF data---but no optimum data?

OK .. optimum is what the point of the calculation is all about. When you start with a particular runway, you don't know what the optimum is going to be .. although, for a Type with which one is familiar, an educated guess is not out of the question ..

(a) first determine the goal. Is it maximum weight ?, a certain pad of (ASDA-ASDR) ? ... whatever

(b) second use the AFM charts or software, as appropriate, to iterate TOW for the conditions until the goal is achieved

Repeat this for the range of conditions (usually OAT and W/V) desired

The specifics of how one goes about the actual calculations will be determined by the presentation in the AFM or the degree of flexibility associated with the software input.

Am I getting closer ?

[mutt]

optimize your V speeds? if you have BFL and UBFL data or is it too cumbersome or do any other caveats apply?In theory, yes, it can be done by input selection, but you would have to list the speeds with the weight.

During my Performance Course, many many years ago, I recall that a couple of seconds or so were factored into the numbers to allow for pilot recognition/response time of an engine failure.. But do these regulations APPLY TO YOUR AIRCRAFT! Its all to easy to remember what we were taught in Perf A, but the reality today is quite different.

Mutt

[Pugilistic Animus]

JT and Mutt---between the two of you-I have my question answered in sufficient detail---I just like learning this stuff--I don't have an opportunity to use this stuff right now---but I enjoy the topic a good deal:8--thank you both for the responses I've learned a lot


Thanks,

PA

[TwinJock]

Yip. I think that each operator has their own way of looking at this. The problem comes when you are involved in a high speed abort situation, and things do not go well for you. The bean counters will be the first to kick you in the wallet!

My technique on the B777 - the ENGINE FAIL call is inhibited at V1 - 6 kts, which I think is the 1 second included for recognition of the failure. I remove my hand from the thrust levers at about 6kts below V1 speed. When you ask for guidance from the company however, it is stated that you hand should only be removed from the thrust levers at V1.

Mmmmmm!

[Pugilistic Animus]

read the thread!---why does everyone know more than Boeing:uhoh:

[cptpilot737]

We call " GO " 3 knots before V1, Company procedure......

[Pugilistic Animus]

why does EVERY ONE:* know more than MR. BOEING:confused::confused::confused::uhoh:





:(

[Jaxon]

why does EVERY ONE:* know more than MR. BOEING:confused::confused::confused::uhoh:



It sounds like you figure you are the torch bearer of sanity. :ok:

Boeing is safe (and unambiguously correct) in making the firm statement about passing V1 and lever position/continued takeoff, but making a firm directive upon when a human should make a callout for affecting this purpose is not, nor ever will be, a hard and fast scientific calculation.

We want the pilot flying to know when his option to reject has expired (yes, of course, at and after V1). The only way for that thought to actually hit that pilot's brain in a timely fashion is for the non-flying pilot to get the sound waves in motion toward his ears BEFORE V1 in enough time for his ears to send that signal to his brain and for his brain to have sufficient time to register and recognize that call out. Some small margin before V1 is obviously required to do that to be the most accurate and compliant with the V1 decision.

Boeing takes responsibility for the science of their creations, beyond that, they merely help as much as reasonably possible and within their own lawyers' restrictions against exposure from creating over-reaching and rigid rules in the area of human factors.

[airfoilmod]

Doesn't Bill say Brakes on levers back by V1??

Airfoil

[Pugilistic Animus]

Airmanship requires that the PF be refrenceing his OWN ASI and to ALWAYS be READY for WHAT ever---WHENEVER

I DON''T CARE IF THE PNF CALLS V1 ON TOUCHDOWN!!!!!!---, the question's ARE U READY---- YES I'M READY {Barbara Mason's Words not mines}

at TO it's SP OPS:eek:

I WONT REST ON THIS PARTICULAR TOPIC and I'm not tired:zzz:

Yo jamas sufri, no jamas llore---
hasta que te conoci .. vi la vida con dolor---no te miento fui feliz aunque muy poco amor---y muy tarde te comprendi que no te deberia amor---porque a pienso en ti mas que ayer mucho mas----da da dada da dum


Westinghouse:ouch:

[airfoilmod]

la linea esta finale, no? Vamanos a Jett Blasto.

Aerojolio

[Pugilistic Animus]

Yeah AFM===They'd all thought I'd break [brake] like Mr. Glass:}:}:}






PA:)

[Denti]

As mentioned above, the auto-V1-callout available on some of bill boeings models calls out V1 just a few knots before V1. Gives you a hint how to do it yourself if that feature is not available, doesn't it?

[OutOfRunWay]

Yes, Mr Bong says, the descision must have been MADE AND IMPLEMENTED at v1.

Everyone remember: decide to reject before V1, you are cheesing off the bean counters. Decide to reject after V1, you are cheesing off (Insert favorite Deiety here), and I know which I would rather do.

[Centaurus]

I'm one of those who responds with a thank you or precedes with a please

Professionally quite unnecessary and worthy of the accusation of verbal diarrrhoea. Perhaps this type of nonsense is why your company requires a call by the PM of degrees of body angle rotation. Similar sentiments apply to those pilots and cabin staff who precede almost every PA with "Ladies and gentlemen, Boys and Girls..." Simply YUK!....

[Pugilistic Animus]

PLEASE ALLOW MR. BOEING TO CALL WHATEVER HE PLEASES HE KNOWS EXACTLY HOW MUCH PLAY YOU HAVE AROUND VEF--DO YOU?:=--- A PERFORMANCE ENGINEER SUCH AS MUTT DOES HOWEVER---AND WHEN MR. B'S AFM SAY AT V1 ---THE AT VEE WUN--IT SHALL BE!!!!----ALL THE WONDERFUL NEW IDEAS IN AVIATION:eek:


LESTER:E

[Pugilistic Animus]

Everyone should apply for a consultancy at Boeing, Airbus or Piper---but I think you'll only Get hired by the Pitts company--because this V1 nonsense is the Pitts:}:ugh:


Lester Wascomat:8:E

[Pugilistic Animus]

Centaurus, with all due respect Sir--- it has always seemed that Guppy is also a very experienced aviator--he has developed admirable airmanship--and is vastly experienced and in the US fars---An ATP--Must!--have a certain moral and ethical character--and he displays this--He is a Gentleman---Aviators are supposed to be---I'm sure He' Not on O'HARE Ground Greeting the Controller in the most formal way:hmm:

PA:)


Guppy,

Strainin' at Gnats and Wolfin' down the Elephants:(

PA--GE maintainance--:ooh:


yo jamAs sufrI--- yo jamAs llorE ---yo era muy feliz Pero,...Pero te encontrE---dada da dada da dum do ao doo doo:ok:

[galaxy flyer]

Speaking of callouts, I didn't like all the military ideas, but simple callouts were a good one. In MAC, it was "GO" at decision speed, "ROTATE" at rotate and that's it! We didn't do an airspeed check, but should have. Even that doesn't need both "ALIVE" and "80 KNOTS", one should be sufficient. "STOP" prior to decision speed would be better than "ABORT, ABORT, ABORT" our mob uses, too.

GF

[Jaxon]

Everyone should apply for a consultancy at Boeing, Airbus or Piper---but I think you'll only Get hired by the Pitts company--because this V1 nonsense is the Pitts

If you are so upset at the close up look at V1, why did you create the thread?

Its a mystical make believe world you make when you believe everybody else is cracked but you. I hope it is at least a comfortable place.

The science lends itself to getting boiled down to a simple and clear declaration/instruction/calculation. What you seem to refuse to accept is the far less precise application of the human factor that works to apply the science. You asked for the up close focus on the issue, I am sorry you feel your instigaton of the whole affair to be "the pitts".

[Pugilistic Animus]

I didn't create this thread--I already know what to do -:ouch:


Because I'm a mean {JUDGE}:}


Lester:E

[Jaxon]

Ah yes, so you didn't (ooops).

So... it is a comfortable place, yes?

[Pugilistic Animus]

Yes,---very :E



The Honorable

Judge L. Westinghouse:E

[FlightDirector7]

But isn't V1 a conservative figure on the RTOW charts ? V1 will cater for stopping performance (be it Wet or dry) even if the decision to reject is made at V1, and initiated say 2 knots above. Yes i do agree that the decision to reject 5 knots before is always better, and one must always be Go-minded above it, but would i be wrong in saying V1 is very conservative on the charts ?

[PEI_3721]

FlightDirector7 “would i be wrong in saying V1 is very conservative on the charts”

When you consider all of the variables then there may be no margin at all.
First to clarify some points in your post in case I misunderstood them: wet V1 is not the same as dry V1; you require more distance to stop on a wet runway. The decision to reject must be taken before V1, and the RTO first actions commenced at or before V1; the aircraft may not start decelerating until a later higher speed.

Some performance engineers (manufacturers) believe that the RTO distances are too close to the limits. This is particularly so when considering a wet runway.
As with landing performance, a single friction value associated with wet conditions is assumed in the RTO calculations. This value may not cover the wide range friction seen in service, e.g. increasing depth of water up to ‘contaminated’ (3mm), different surfaces – smooth vs grooved, concrete vs tarmac. Then there is paint and rubber deposits on the runway to consider, brake and tyre condition, and accuracy of wind information – the friction associated with the previous conditions are not know to the crew.

Where ever possible my SOP was to use the wet V1, I chose to accept a lower screen height in the rare event of an engine failure at V1 – go minded. This in my judgement entailed less risk than a stop from just before a ‘dry’ V1. The tricky problem is when the runway is wet (you need the wet V1), but would like to reject earlier – which is not possible if already at the Vmcg limit; be very, very sure about your stop decision – think about the situations (briefing), reasons, warnings, and actions carefully before take off.
The problem is heightened with poor/marginal runway conditions. Again comparing with landing; some runways are classified 'slippery when wet', where the operators are expected to take account of this; this warning (classification) is important during takeoff as it will effect an RTO – but who actually considers that?

[FlightDirector7]

Hi PEI 3721,

I agree with all your comments. When i had mentioned the V1 speeds "be it wet or dry" in my last post i had known that they would be much lower in the case of wet for all the reasons you had mentioned and more ofcourse. As a matter of fact, on the A319/320/321, i have seen V1 speeds up to 12 knots lower than that of a dry runway at certain airfields. My question was simply to ascertain whether V1 on RTOW charts are so critical that they don't factor in reaction time even if you reject slightly above V1. Lets take a case where there is no split between the V1 and Vr, yes rejecting now is pointless as you might as well get airborne. But if you have a split of say 8-9 knots between V1 and Vr, due to climb gradient performance, its a more serious matter accelerating to Vr after having lost an engine. Leaving aside the legal implications of rejecting slightly above V1, my question was does that speed leave an margin for you being a conservative speed, or is it a GO speed ?

[Denti]

Was allways trained to see V1 as a go speed. At least the training tools from boeing we use pretty much stress the point to consider it as such.

[FE Hoppy]

FD-

V1 is the speed at which the first action to stop must take place.

Your confusion comes from the fact that in the certification process time is added for each of up to 3 actions to take place. Brakes, Speed brake, Idle. The time taken to complete these actions is then expanded in the AFM to allow for the dumb pilot who can't find the Speed brake lever or is slow to brake or select Idle.

This does not mean you have thinking time above V1, it means you have already decided to stop but have a few seconds to actually do it.


I honestly believe that some of the discussions on this subject have clouded a very straight forward operating philosophy.

[Pugilistic Animus]

You Can't use WET figures on DRY RWY:ugh:-----Why:confused:

[Pugilistic Animus]

There are several reasons-- I avoid--- if at all possible flying with the airlines now:\

[Ali Chapussy]

"I honestly believe that some of the discussions on this subject have clouded a very straight forward operating philosophy."

I agree with the above quote several posts back.

Always said V1 by V1. No "decision" needs be made at v1, no action taken, all you have to do is continue doing what you are doing.....taking off, and if an engine has quit in that very unlikely time between inside the human reaction time before hearing V.....and V1 occurring, then put in some rudder to keep the nose pointing towards the middle at the far end and wait for "rotate". No need for concerns as to whether or not that inbuilt 2 seconds exists and/or is applicable to my airframe type and if it is, does that mean I should/could use it? Christ no anyway but there is no need to "react" to anything anyway. The reaction is sit on your hands, wind the clock, take a deep breath, swear a bit, and continue the takeoff.

The argument here about when to say it is irrelevant, immaterial and beside the point your honour, as the Capt (in my outfit it was always the Captains hand on the thrust levers) you knew when you were approaching V1, and as soon as you heard the commencement of the words V1, you knew that your decision was made - no decision to make, just keep going.

What else are you going to do? "well your honour I heard him say V...... but thought he was about to tell me "Very nice takeoff roll so far skipper" so I decided to abort due to.......and ran off the end at 60kts" No of course not.

No decision to make - its been made for you - GO son go.

[Pugilistic Animus]

Ali [excellent name] one of the most creative---thanks---I needed some backup:ouch:


I don't know what's wrong with them ---perhaps too many hard arrivals:}
:D:D:D

PA

[FlightDetent]

You Can't use WET figures on DRY RWY:ugh:-----Why:confused:

You actually can. TOW for wet must never be higher than max allowable TOW dry. But before you do, please consider:

WET figures are calculated with the decceleration force of available reverses. On the other hand, DRY figures are based on brakes only. Hence on a DRY-figure takeoff, at V1 you start to brake and should stop by runway shoulder. If you use the reversers, your stopping distance will be (much - not true) somewhat less than that (calculated). Using WET figures relies on both brakes and reversers so there are no more aces left up your sleeve.

WET figures assume minimum screen height of 15 ft. On the other hand, DRY figures require minimum of 35 ft. For balanced field, this translates to lower V1 figure to accomodate for longer braking distance on the wet tarmac.
Provided the runway is indeed DRY: should you use WET figures and elect to continue at V1, acceleration from a lower than required V1 will take longer and cover greater distance to lift-off, clearing DERA or CWY end by 15 ft. If you had used DRY V1, ENG failure (birdstrike) at the identical point of tkof roll would be still before V1 - so stopping is now a newly available option (with the extra comfort of using reversers not accredited within your ASD calculation); while an ENG failure at (the higher) dry V1 would give you 35 ft margin over the fence. The NW strut itself is 5 ft high on my aircraft.

FD (the un-real)

PS: Enter "Old+Smokey" is the search field.

[FlightDirector7]

Well, There we have it ! Case closed as far as i'm concerned :D

[A37575]

and wait for "rotate". No need for concerns as to whether or not that inbuilt 2 seconds exists and/or is applicable to my airframe type

Be careful there. The word from the PNF of "Rotate" is purely a back up and not a order, although depending on how loud it is called it is often taken as an order rather than simply a speed on the PNF's ASI.

You should commence rotation at VR on your own ASI - not on a call from the PNF. In the simulator we often see delayed rotation by the PF because he unconsciously waits then acts on the "Rotate" call from the other side of the cockpit. Often see 5-15 knots delay in rotating especially in the engine failure case simply because the PNF forgot to call and the PF waited and waited and waited.

[A37575]

If you use the reversers, your stopping distance will be much less than that (calculated).

On a slippery runway yes. On a dry runway there is very little difference between stopping distance with full brakes and full brakes with reverse. Of course it perhaps depends on the aircraft type but in the 737 the difference on a dry runway is only 170 feet with one reverser operative and 180 feet with both thrust reversers operating.

[FlightDetent]

Thanks for pointing that out. There is no ASD charts in my books, but landing charts indicate dual reverser benefit of -3 per cent for A320. At 76t (max TOW) the actual landing distance with full manual braking indicates 1010 m showing a mere 30,3 m benefit for both reversers.

[Pugilistic Animus]

Yes, you may use the more conservative of the wet {WATES}--but---you must use the DRY Vee-speeds :zzz:

Playing TP--with the WET RWY figures:eek::=

Btw--I just do a user name search;)


PA

[Pugilistic Animus]

The problem with using Wet runway data on a Dry runway is that it's illegal.

The normal rules require that a 35 ft screen height be obtained within the TODA, and that one means of retardation (inevitably reverse thrust) be kept in reserve. That's the rules.

Then, along comes a DISPENSATION for Wet runways (Wet, not Dry or Damp) which allows the use of Reverse Thrust, and allows for a reduced screen height to 15 ft. The dispensation is allowed to be used, ONLY IF THE RUNWAY IS WET!

The dispensation entirely removes the ONLY spare performance capability remaining on a Dry runway for a RTO, and significantly reduces obstacle clearance for the continued Takeoff.

There's absolutely nothing wrong with using the more limiting of the Wet and Dry RTOW for any runway condition (except Contaminated), provided that the chosen Thrust and V-Speeds used with the actual weight are for the actual prevailing conditions, i.e. Dry (including Damp) or Wet.

Regards,

Old Smokey
http://www.pprune.org/forums/images/statusicon/user_offline.gif http://www.pprune.org/forums/images/buttons/report.gif (http://www.pprune.org/forums/report.php?p=3791088) http://www.pprune.org/forums/images/buttons/reply_small.gif (http://www.pprune.org/forums/newreply.php?do=newreply&p=3791088&noquote=1)
Old SmokeyView Public Profile (http://www.pprune.org/forums/member.php?u=90911)Send a private message to Old Smokey (http://www.pprune.org/forums/private.php?do=newpm&u=90911)Find More Posts by Old Smokey (http://www.pprune.org/forums/search.php?do=finduser&u=90911)Add Old Smokey to Your Buddy List (http://www.pprune.org/forums/profile.php?do=addlist&userlist=buddy&u=90911)



Some Facts given by someone much more knowledgeable in this area than I---:)

PA

[FlightDetent]

Apparently you cannot then.:oh:

[Denti]

As in all cases it depends on the authority under which rules you operate. We used for several years wet figures on any conditions except contaminated and reduced braking. That was approved from the local authority for operation under JAR OPS 1.

We only switched away from that when we introduced an EFB tool that of course can calculate values much closer to any relevant margin and therefore has to use dry figures on dry runways to allow further derate, higher assumed temperaturs or simply carrying more weight. Now we enjoy the fun of rotating at the numbers.

[Pugilistic Animus]

JAR OPS 1 sounds very similar to part 121-in that Air carrier OpsSpecs must be approved by an official [in the FAA --a principle operations inspector POI]---but in this case it appears that the official who allowed that didn't understand or chose to disregard the law:\

[SNS3Guppy]

Professionally quite unnecessary and worthy of the accusation of verbal diarrrhoea. Perhaps this type of nonsense is why your company requires a call by the PM of degrees of body angle rotation. Similar sentiments apply to those pilots and cabin staff who precede almost every PA with "Ladies and gentlemen, Boys and Girls..." Simply YUK!....


Unnecessary? That's why it's called "courtesy."

Verbal defecation, you say? Hardly.

We don't make cabin announcements.

The pitch angle call is part of the standard callouts, and it's a target reference attitude for a V2 climb with an engine failed; a reference and nothing more. It's not intended to be the angle to which one pitches on all engine departure. It's a parameter provided by our computerized onboard performance system which provides all the TOLD data for the departure, and yes, it's part of every standard takeoff procedure at our company.

I didn't invent the company standard procedures, but I do follow them.

[Pugilistic Animus]

with the amazing pedagological power of youtube--I found and admirable example of Clear SOPS and well executed takeoff procedure--

Look at the Pro's:}

http://www.youtube.com/watch?v=M3rBW94EPyc


PA