Huge distance between V1 and VR

[ersh2k4]

Hello everyone!

I`ve been flying a >50 ton commercial jet for a few months now and there is something that is bothering me for a long time.

Sometimes, on a long runway takeoff (>3000 meters) with normal parameters (normal weight, not too heavy not too light, normal temperature, etc.) the V1 and VR are too far from eachother, for eg. V1 115kt and VR 135kt

in all cases, i`ve discussed this with the CA, and they all have the same doubt; could this v1 speed just be wrong?

Cheers!!

[BOAC]

Don't think so - it would appear your company uses performance biased towards 'Vgo' rather than the 'traditional' which would probably have V1 and Vr coincident on a 'long' runway.. .

[frankthefrowner]

Not sure about your plane but on the Gulfstream V I fly with Honeywell boxes, you could run into this issue if you do all the takeoff perf calculations before the takeoff fuel load is manually or automatically entered.

[sabenaboy]

There's a lot of interesting info for you in this thread (http://www.pprune.org/tech-log/478624-use-toga-flex-speeds.html) and particularly in this post (http://www.pprune.org/tech-log/478624-use-toga-flex-speeds-2.html#post7059572).

[FLEXPWR]

On the plane I fly (320) depending on which performance equipment you use (EFRAS software for example), for the conditions you describe, there is a wide range of V1 speeds you can use. This will help determine as well how much distance remaining to the end of the runway. Your company may chose to select the lowest V1 as default?

[mutt]

if you do all the takeoff perf calculations before the takeoff fuel load is manually or automatically entered. Why would you do the performance calculations with an incorrect fuel figure?

[FLEXPWR]

mutt, I think he meant to input some estimates before getting the actual data, just to see what possibilities are at hand.
On the bus, you can insert estimates values for weight, CG, fuel, to get an idea of the flap/maneuvering speeds, cruise altitude you'll be able to chose, etc.

[BOAC]

It's ok, guys - I suspect SSG has been breeding again.

[ersh2k4]

oh that explains a lot...

i`ve always considered v1 as been fixed, based on the variables you have, using ALL runway distance available to a full stop.

so what i still dont understand is, why would we limit V1 in order to be able to stop with some distance remaining? I mean, in a real emergency event, i would feel very uncofortable to continue the takeoff knowing i could stop the aircraft after V1...

i dont get it!

[rudderrudderrat]

Hi
I mean, in a real emergency event, i would feel very uncofortable to continue the takeoff knowing i could stop the aircraft after V1...
i dont get it!
That's easy to fix. Just do take offs from limiting runways.

[john_tullamarine]

why would we limit V1 in order to be able to stop with some distance remaining?

perhaps we might prefer that to stopping with some grass behind us ?

Putting aside facile comments, the problem comes down to one of risk and risk management for managing an engine failure.

By far the greatest risk during takeoff is a critical accel-stop manoeuvre. The margins (especially pre-amendment 42) are such that one should prefer other alternatives.

The continued takeoff, on the other hand, offers far lower risk, especially as the aircraft progresses away from the runway and the gross-nett delta provides an increasing terrain clearance pad.

Caveats -

(a) for very lightweight takeoffs operating to min speed schedules, the proximity to the real world Vmcg may make a continued takeoff very difficult

(b) in the real world, the range of failures and problems which might warrant rejection aren't necessarily embodied in the AFM certification data.

[Anotheravatar]

You have to understand that airline pilots are taught that all planes fly after V1, like there is some electromagnetic cushion provided by the airspeed indicator that defies all logic and physical reality.

That way, when the pilots rotate after V1, they are completely impervious to the fuel truck stuck in their landing gear, the birds that went into the engines, the 02 canisters exploding in the nose, the terrorist that took out the flight controls, the jack screw that wasn't properly inspected, the ice they didn't clean off, the 152 that slammed into the cockpit, the cargo door that just opened, the copilots who's seat that just went full rear(but he's still flying -lol), the FOD that takes out your left engine, the deflating or blown tires...on and on...

You see, that way, you can use less power on the roll, less power = longer overhaul times, the company saves money. They are happy, you have a job, your happy.

See how this works?

So the next time you when you push the throttles up only part way, and burn up all the runway to VR, don't think about this stuff. I will only make your head hurt, and you won't be considered a team player.

[john_tullamarine]

airline pilots are taught that all planes fly after V1

While there might be a certain familiarity to the style of the last post, I think that the above comment is a tad in the throw away line department.

I think it more probable that reputable airlines emphasise the benefits of SOP whilst giving enough information for line pilots to exercise a modicum of discretion.

I recall a line check on the B727 years ago as a young sprog wherein at the debrief the very wise greybeard checkie observed "John, always keep in mind the invisible ink writing on page two of the Ops Manual - To Be Read With a Bit of Commonsense "

[Anotheravatar]

So your saying you would do a post V1 abort if the conditions warranted?

[john_tullamarine]

So your saying you would do a post V1 abort if the conditions warranted?

Perhaps you might cite a postulated scenario rather than waxing lyrical in generic manner ? The protocol is to adopt SOP procedures unless they, clearly, are not going to work.

[Anotheravatar]

Find me an airline pilot willing to bust a SOP because it 'clearly won't work' and we can talk scenarios. Airlines hire guys that follow orders, not think out of the box.

[galaxy flyer]

Not again, I'm getting too old for this "mulligan" of the V1 reject thread.

OR,

Is it Goundhog Day on Pprune

GF

PS: if you really think pilots are hired to take orders, you might research the 1989 strike at TAA and Ansett.

[john_tullamarine]

Airlines hire guys that follow orders, not think out of the box

Perhaps I come from a superseded variant of airline ? .. as it happens, one of the aforementioned airlines.

Not again,

Probably getting to that time of the thread, I guess.

[de facto]

Popcorn and coke (drink that is) out and ready:E

[Brian Abraham]

Popcorn and coke (drink that is)You don't need the other kind de facto. Reading post by Anotheravatar (err....SSG) you would swear you already were on the other stuff.

Interesting, on another thread he says,
I don't plan on spending my whole life in a cockpit.I wasn't aware he had spent any of his life in a cockpit.

[paperdragon]

What about the more obvious explanation, does Your companys perfomance computer default improved climb?? In all other cases a scenario like this would give me the creeps, I would probably send a question up in the organisation to the performance engineer.

Happy landings:)

[ersh2k4]

perhaps we might prefer that to stopping with some grass behind us ?Perhaps i would prefer the grass than taking a 50 ton aircraft off the ground with an engine blown or on fire. but hey, thats just me not willing to fly with an acft on fire.

nevertheless i said use the entire runway available . i havent mentioned any grass

im sorry but anticipating a V1 for any reason just does not make sense to me. yet!

So your saying you would do a post V1 abort if the conditions warranted? are you kidding me?

does Your companys perfomance computer default improved climb??But than it would be exactly the contrary, since an improved climb configuration would give you higher both V1 and VR and get them closer together.

the only thing i cant think about would be a brake energy speed limitation?

[john_tullamarine]

nevertheless i said use the entire runway available . i havent mentioned any grass

Unfortunately, you are looking at a grey subject in black and white terms .. that's probably not the optimum approach from a risk management perspective.

[Broomstick Flier]

Hello ersh2k4,

Being aware which type you have in mind, i.e the E190/E195, the answer for your question can be found in a couple of places.

When running the EPOP (this is the performance calculations software made by Embraer, for our friends not familiar with the E-jets) software and having the take-off speeds page ready, give a look into the "INPUT SUMMARY" tab. There to the end of the page you will find some information like this:
V1/Vr = ....
V2/Vs = ....

They call them V1/Vr ratio (and V2/Vs ratio) and taking a look in the former pair, the available results are:
Optimum V1, Fixed, Balanced V1, Min V1 and Max V1.

Experience so far has shown me that Optimum V1 is the more likely result you will get and it is calculated based on the Optimum V1/VR ratio in order to get the higher RTOW possible. Please note that in older versions of EPOP we could choose the ratio but I understand that on more recent versions this is done automatically by the software based on conditions.

Safe flights,
BF

[bubbers44]

Remember the British 737 that aborted and caught on fire about 20 years ago? Maybe if you are at V1 it might be safer to keep the fire behind the engine in flight and have the fire trucks waiting when you land after performing your checklists and briefing the FA's. Maybe by then there will be no fire and if so the trucks will put it out. Usually once the fuel is shut off there is nothing left to burn.