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wxman11
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Rolling Takeoff B787-9 Expand CG Area

Mon Apr 20, 2015 6:53 pm

Hi folks,

Is there any takeoff restriction on the B787-9 in which the takeoff CG is affected? Does the pilot have to change their takeoff from a normal takeoff to a rolling takeoff if the CG is out of limit?
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Mon Apr 20, 2015 7:02 pm

Quoting wxman11 (Thread starter):
Is there any takeoff restriction on the B787-9 in which the takeoff CG is affected? Does the pilot have to change their takeoff from a normal takeoff to a rolling takeoff if the CG is out of limit?

If the CG is out of limit, you don't takeoff. It has nothing to do with rolling or static takeoff.
 
mmo
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RE: Rolling Takeoff B787-9 Expand CG Area

Mon Apr 20, 2015 8:01 pm

Quoting wxman11 (Thread starter):
Does the pilot have to change their takeoff from a normal takeoff to a rolling takeoff if the CG is out of limit?

Rolling takeoffs are the preferred technique for "normal" conditions. As has been stated already, if the CG is out of the envelope, you don't take off.
If we weren't all crazy we'd all go insane!
 
trijetsonly
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RE: Rolling Takeoff B787-9 Expand CG Area

Wed Apr 22, 2015 2:38 pm

I don't know about the 787-9 but in the 787-8 there is definitly an increased CG-Limit for rolling takeoffs!

It is applicable between weights of 229500 lbs and 428300 lbs TOW.
Using the Rolling Takeoff Procedure allows you (depending on the weight) up to 7% more aftward CG.

I guess the reason is in the tipping moment during breakes release when there is thust applied.
Happy Landings
 
mmo
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RE: Rolling Takeoff B787-9 Expand CG Area

Wed Apr 22, 2015 5:02 pm

Quoting Trijetsonly (Reply 3):
I don't know about the 787-9 but in the 787-8 there is definitly an increased CG-Limit for rolling takeoffs!

I do realize that, but the question was

Quoting wxman11 (Thread starter):
Does the pilot have to change their takeoff from a normal takeoff to a rolling takeoff if the CG is out of limit?

and the answer is still you can't takeoff if you are out of the CG envelope. Where I work, the CG calculation is based on a static takeoff as it's the most restrictive. If there is an operational requirement to have a very rear CG then the crew is notified to ensure a rolling takeoff is accomplished. However, in 30 years of commercial flying, I can count on one hand the number of static takeoffs I have accomplished.
If we weren't all crazy we'd all go insane!
 
hivue
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RE: Rolling Takeoff B787-9 Expand CG Area

Wed Apr 22, 2015 5:25 pm

Quoting mmo (Reply 4):
If there is an operational requirement to have a very rear CG then the crew is notified to ensure a rolling takeoff is accomplished.

Does this imply that a marginal in-limit CG can potentially be put out-of-limit in a static takeoff? If so, is that considered operationally acceptable?

EDIT: In other words, aren't CG limits calculated on the conservative assumption that the crew might forget and do a static TO?

[Edited 2015-04-22 10:34:08]

EDIT2: Never mind. After a little thought I answered my own question (I think). The problem isn't sloshing fuel but rather the chance that improperly secured baggage/cargo could come loose and shift aft.


[Edited 2015-04-22 10:41:08]
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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zeke
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RE: Rolling Takeoff B787-9 Expand CG Area

Wed Apr 22, 2015 6:21 pm

Quoting hivue (Reply 5):

Reading between the lines it is the low speed Vmcg limit which is the issue. Using a rolling takeoff they have aerodynamic control as well as nose wheel steering to control the engine failure. Low speed rejected takeoffs are not that easy to handle.

The other option used on some aircraft is to derate the thrust, so you are effectively taking off with less thrust, this lowers Vmcg.
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DocLightning
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 4:30 pm

Quoting mmo (Reply 4):
and the answer is still you can't takeoff if you are out of the CG envelope. Where I work, the CG calculation is based on a static takeoff as it's the most restrictive. If there is an operational requirement to have a very rear CG then the crew is notified to ensure a rolling takeoff is accomplished. However, in 30 years of commercial flying, I can count on one hand the number of static takeoffs I have accomplished.

Really? As a passenger I've been on several.
-Doc Lightning-

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vikkyvik
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 4:57 pm

Quoting zeke (Reply 6):
Reading between the lines it is the low speed Vmcg limit which is the issue. Using a rolling takeoff they have aerodynamic control as well as nose wheel steering to control the engine failure. Low speed rejected takeoffs are not that easy to handle.

Aren't most rolling takeoffs probably started at something like 5 to 15 knots? Does that really make a difference to Vmcg? There's barely any aerodynamic control at such low speeds.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 5:20 pm

I believe that it is com

Quoting DocLightning (Reply 7):
Really? As a passenger I've been on several.

You don't any clue as what tower has directed the aircraft to do. More often than not, it's clearance to "line up and wait" or maybe the tower has issued a "cancel your takeoff clearance" at the last minute the aircraft has entered the runway, if even by a foot or so. It's all very dynamic and trying to read anything into the process from row 6A is sketchy at best. Controllers want to move traffic so it's not the least bit uncommon to have them move you along in the line. Sometimes they will even add a comment like "aircraft on a three mile final, be ready when I release you" probably not a legal clearance but get the idea. Note they will not use the word "takeoff" in that comment, for fear of a misunderstanding.

Low Visibility Operations with an RVR below 1200 require a static takeoff. Don't bet your last paycheck on that RVR value but I'm pretty sure that is the number.

In short trying to figure out what is happening from a cabin seat is like going to trial with none of the facts at hand. It's only natural that those of us who have a keen interest in aviation and airliners in particular try to put themselves in the cockpit, but it's usually a risky deal at best.  
 
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zeke
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 5:37 pm

Quoting DocLightning (Reply 7):

Must admit I have done a my fair share of aft CG takeoffs out of JNB to increase payload for hot and high.

For those who do not understand the correlation, the horizontal tail plane produces down force to counter the lift/weight couple (center of lift and center of gravity have a moment arm), which the aircraft must produce extra lift to takeoff, having an aft CG reduces the amount of down force required on the tail plane, and thus the lift can be converted into extra payload.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
mmo
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 6:58 pm

Quoting BravoOne (Reply 9):
Low Visibility Operations with an RVR below 1200 require a static takeoff. Don't bet your last paycheck on that RVR value but I'm pretty sure that is the number.

They are not in any Ops Specs I have operated under so I don't think it is an actual regulatory requirement. There are some airlines that require a static after de-icing but I have not flown under them. To be honest, they are quite un-nerving for most pax.
If we weren't all crazy we'd all go insane!
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 7:09 pm

mmo,

I don't mean hold the brakes and run up before starting the roll I just mean staring the takeoff from a stand still position. The other possibility would be the engine run up prior to brake release to shed fan ice. That could be misconstrued as something else?
 
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SAAFNAV
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 7:56 pm

Boy, that's something I'll miss when I get to airlines one day..

Light Aircraft, full power against brakes, max effort rotate and climb out at Vr+10 until obstacle height....

Most pax would have a heart attack though.
CFI/Gr. III, L-382 Loadmaster, ex C-130B Navigator
 
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Stitch
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 10:09 pm

Quoting DocLightning (Reply 7):
Really? As a passenger I've been on several.
Quoting BravoOne (Reply 9):
You don't any clue as what tower has directed the aircraft to do.

Never flew on United when they offered "From the Cockpit" on Channel 9, I guess.  
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 10:39 pm

Quoting Stitch (Reply 14):
Never flew on United when they offered "From the Cockpit" on Channel 9, I guess.  

To the contrary I have flown on UAL more than most  I just don't sit back and think I have it all figured out... There so much more to the BIG Picture!
 
vikkyvik
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 23, 2015 11:33 pm

Quoting BravoOne (Reply 9):

I wonder if there's some terminology confusion here. I thought a rolling takeoff was one where you enter the runway and proceed to takeoff without stopping, whereas a static takeoff is when you enter the runway, stop, then start the takeoff.

It seems like what people are really talking about is running up the engines while holding the brakes (so stopped), versus releasing the brakes and running up the engines, so accelerating while spooling up.

Any help?
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri Apr 24, 2015 12:00 am

Quoting vikkyvik (Reply 16):
I wonder if there's some terminology confusion here. I thought a rolling takeoff was one where you enter the runway and proceed to takeoff without stopping, whereas a static takeoff is when you enter the runway, stop, then start the takeoff.

A static is as you have described. (Thank you ) You line the airplane with the center line while coming to a full stop. It has nothing to do with running the engines up unless you are doing an ice shedding run up. The all becomes more critical when using the HUD for a Lo Viz takeoff.
 
vikkyvik
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri Apr 24, 2015 3:54 am

Quoting BravoOne (Reply 17):
You line the airplane with the center line while coming to a full stop. It has nothing to do with running the engines up unless you are doing an ice shedding run up. The all becomes more critical when using the HUD for a Lo Viz takeoff.

OK, but in that case, it should be quite easy to tell if you did a static takeoff from row 6A, I would think.

As another passenger, I can't remember the last static takeoff I've been on, but I know I've been on several. Just not recently.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
mmo
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri Apr 24, 2015 7:21 am

Quoting BravoOne (Reply 12):
mmo,

I don't mean hold the brakes and run up before starting the roll I just mean staring the takeoff from a stand still position. The other possibility would be the engine run up prior to brake release to shed fan ice. That could be misconstrued as something else?

We might be talking semantics. The definition of a static takeoff is parking brake set, takeoff thrust applied to all engines, brakes released. A rolling takeoff is everything else. Regarding the engine runup for icing that is not anywhere near full thrust and personally, I ensure all are brought back to idle. That way you can ensure normal operation...but that is technique only. Even using the HUD on the 787 you can do a rolling takeoff. The 744 with the PVD did not have a requirement for a static takeoff.
If we weren't all crazy we'd all go insane!
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri Apr 24, 2015 11:25 am

yes but not holding the brakes while you run the engines up to high power setting beyond a ice shedding N1,/EPR.

Good morning)
 
mmo
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri Apr 24, 2015 12:07 pm

Quoting BravoOne (Reply 20):
yes but not holding the brakes while you run the engines up to high power setting beyond a ice shedding N1,/EPR.

The run up required isn't that much. However, that's why I qualified what I wrote about the engine runup for icing. It's nice to know the engines spool down and it gives you a change to do a quick scan on the engine instruments. It only takes a few seconds and there is no rush since ATC know what you are going to do. All you really have to do is push the T/L beyond 50% N1 and back to idle and make sure you have good engine indications. I have seen more than one engine continue to roll back. So, as I wrote, it's only a technique but one I strongly recommend.
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jetwet1
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri Apr 24, 2015 12:41 pm

I must really be missing something here, I did about 100 flights out of LAS last year and I can count on one hand the number of rolling take offs we did, literally 95% were pull onto the runway, stop, apply thrust, then release brakes. About a 50/50 mix of DL 320 and 739's.

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DocLightning
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RE: Rolling Takeoff B787-9 Expand CG Area

Sun Apr 26, 2015 4:56 am

Quoting BravoOne (Reply 9):
You don't any clue as what tower has directed the aircraft to do.

Well, in three, the captain warned us.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Sun Apr 26, 2015 6:36 pm

Quoting mmo (Reply 19):
We might be talking semantics. The definition of a static takeoff is parking brake set, takeoff thrust applied to all engines, brakes released. A rolling takeoff is everything else. Regarding the engine runup for icing that is not anywhere near full thrust and personally, I ensure all are brought back to idle. That way you can ensure normal operation...but that is technique only. Even using the HUD on the 787 you can do a rolling takeoff. The 744 with the PVD did not have a requirement for a static takeoff.

We are beating his one to death. I have never suggested that you can't make a rolling takeoff with a HUD installation. I'm pretty sure Boeing "embraces" the static low visibility takeoff as I got gigged on it when taking a Boeing 777 61:58 check. I'll try a couple of TCEs or Flight Technical and see what they say. BTW "Static is static as in stopped for what ever reason.

I have never seen a PVD installation in a US airline operation. Seems to be a BA thing that got handed down to Singapore and Cathy. I was in a former Qantas 767-300 a couple months ago and that was the first time I had actually seen one work. Very nice!

[Edited 2015-04-26 11:40:55]
 
BoeingGuy
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RE: Rolling Takeoff B787-9 Expand CG Area

Mon Apr 27, 2015 10:40 pm

Quoting DocLightning (Reply 23):
Quoting BravoOne (Reply 9):
You don't any clue as what tower has directed the aircraft to do.

Well, in three, the captain warned us.

With the exception of ice shedding I'm not aware of doing a full static run up for any reason other than a short runway. They are sometimes done at SNA and I believe MDW. I was a passenger for one at AEP on an AR MD-80.

They do them at Lukla, Nepal and Saba for obvious reasons if you know those runways.
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Tue Apr 28, 2015 9:26 am

As MMO previously posted no one is doing a "full static run up" for ice shedding procedures. Not required on any airplanes that I know of.
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Tue Apr 28, 2015 8:07 pm

Think I' going to have to eat Crow as I cannot find and requirement for the static takeoff in low viz operations. Appears to be an operator specific requirement and no buried anywhere in the OpSpecs, TERPS or there regulatory data. I owe MMO a drink of his choice!
 
BoeingGuy
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RE: Rolling Takeoff B787-9 Expand CG Area

Tue Apr 28, 2015 11:34 pm

Quoting BravoOne (Reply 26):
As MMO previously posted no one is doing a "full static run up" for ice shedding procedures. Not required on any airplanes that I know of.

The requirement for ice shedding is to hold up to 60% N1 on some engines. I guess not quite full run up, but close.
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Wed Apr 29, 2015 9:09 am

Quoting BoeingGuy (Reply 28):
Quoting BoeingGuy (Reply 28):
The requirement for ice shedding is to hold up to 60% N1 on some engines. I guess not quite full run up, but close.

Not very close at all and if you were in winter condition with a contaminated runway when you do this procedure a 100% or anything near full power would be hazardous to say the least.
 
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flylku
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 30, 2015 12:25 am

So it sounds like the definition of a static takeoff is, brakes, full power (waiting until a specified power threshold is achieved) then brake release. So, why are they so rare? Is there some added risk, such as FOD ingestion?
...are we there yet?
 
mmo
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 30, 2015 5:49 am

Quoting flylku (Reply 30):
So, why are they so rare? Is there some added risk, such as FOD ingestion?

They are rare for a number of reasons. First of all, on large hi-bypass engines, crosswinds at high power settings with no forward velocity tend to be more prone to compressor stalls due to turbulent air in the inlet. Secondly, takeoff data is based on a rolling takeoff. In addition, the entire experience is noisy and stress inducing for passengers. Finally, you occupy the runway for a much longer period of time thus reducing arrival/departure rates.
If we weren't all crazy we'd all go insane!
 
Okie
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 30, 2015 3:32 pm

Quoting flylku (Reply 30):
So it sounds like the definition of a static takeoff is, brakes, full power (waiting until a specified power threshold is achieved) then brake release

I have not been a passenger on a jet aircraft in which there was a "Static Takeoff"
However I have been at airports where there were multiple runways in use and we would line up on the end of the runway and wait for a proceeding aircraft to provide separation then release the brakes and power up but not static.
I have also seen static take offs on jet aircrafts at demo/airshows but not passenger service.

If you roll back your watch a few decades the static takeoffs were pretty normal in the days of piston engine propeller commercial aircraft. 3's 4's 6's 7's 1049's etc. You would just use up too much runway manually getting the engines equalized. Runways in those days were not lengthened yet to handle turbine aircraft.



Okie
 
BravoOne
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RE: Rolling Takeoff B787-9 Expand CG Area

Thu Apr 30, 2015 3:45 pm

Okie,

Hate to drag this subject through anymore than I have already but I flew the DC6B, DC7C and 1049H , yea I'm old! I cannot recall ever doing what you have just written. Can you be more specific please as this was never "pretty normal". Keep in mind you did engine run ups back in those days and check for any number is issue prior to taking the runway. Also, engine over heating was a real issue, especially in the Connie.
 
hivue
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RE: Rolling Takeoff B787-9 Expand CG Area

Fri May 01, 2015 2:21 am

From the OP:

Quoting wxman11 (Thread starter):
Does the pilot have to change their takeoff from a normal takeoff to a rolling takeoff if the CG is out of limit?

So, following all the discussion above, what exactly is a "normal takeoff."
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.

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