Emirates near disaster on takeoff

KLB said:
The Challenger 300 will go flying. I was playing around with rudder effectiveness and directional control in the sim on V1 cuts. We were trying to hold the centerline as long as we could while keeping it on the ground. It required quite a bit of forward pressure on the yoke. It also takes very little back pressure to rotate during normal circumstances.
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I’ve never tried to hold a Lear on the ground past VR but the 45 at least requires a very positive rotation if you’re properly trimmed.
 
KLB said:
The Challenger 300 will go flying. I was playing around with rudder effectiveness and directional control in the sim on V1 cuts. We were trying to hold the centerline as long as we could while keeping it on the ground. It required quite a bit of forward pressure on the yoke. It also takes very little back pressure to rotate during normal circumstances.
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Roger Roger said:
I’ve never tried to hold a Lear on the ground past VR but the 45 at least requires a very positive rotation if you’re properly trimmed.
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It may seem trivial, but this is why I love this site.

@milleR asks a legit question about trim/flight characteristics. Multiple, informed answers come in, and I learn something completely new about jets that I didn't know before, and probably wouldn't have known no matter how much I read the Turbine Pilot's Flight Manual.

It's a glimpse into the JC of old and I, for one, am grateful.
 
killbilly said:
It may seem trivial, but this is why I love this site.

@milleR asks a legit question about trim/flight characteristics. Multiple, informed answers come in, and I learn something completely new about jets that I didn't know before, and probably wouldn't have known no matter how much I read the Turbine Pilot's Flight Manual.

It's a glimpse into the JC of old and I, for one, am grateful.
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Holding the jet on the ground while accelerating after loss of an engine in a go-situation, assuming runway available to do so and still rotate, can help with directional control upon rotation with asymmetric thrust. No real need to in any centerline thrust jet with the loss of one and continuing, but can be very helpful in non-CL jets. Coming from two jets that already had climb issues on a heavyweight accelerate-go, and having had a loss of thrust on takeoff past Vr once, I didn’t want to add directional control issues at liftoff to it also. Then again, these excess thrust engines that jets have now like the CFM have much more power to them which is nicer for climb, but also more directional control issues to have to correct for when slower.
 
MikeD said:
Holding the jet on the ground while accelerating after loss of an engine in a go-situation, assuming runway available to do so and still rotate, can help with directional control upon rotation with asymmetric thrust. No real need to in any centerline thrust jet with the loss of one and continuing, but can be very helpful in non-CL jets. Coming from two jets that already had climb issues on a heavyweight accelerate-go, and having had a loss of thrust on takeoff past Vr once, I didn’t want to add directional control issues at liftoff to it also. Then again, these excess thrust engines that jets have now like the CFM have much more power to them which is nicer for climb, but also more directional control issues to have to correct for when slower.
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Makes sense.

Is there much asymmetric thrust in a biz jet with rear-mounted engines like a Citation or Phenom? Are those considered centerline thrust since they're so close to it?

I can see the asymmetric thrust situation being an issue on something with wing-slung motors, but it can't be as significant on the tail, right?
 
killbilly said:
Makes sense.

Is there much asymmetric thrust in a biz jet with rear-mounted engines like a Citation or Phenom? Are those considered centerline thrust since they're so close to it?

I can see the asymmetric thrust situation being an issue on something with wing-slung motors, but it can't be as significant on the tail, right?
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It’s definitely there. It’s only really a battle if you get something like an uncommanded TR deployment tho.
 
killbilly said:
Makes sense.

Is there much asymmetric thrust in a biz jet with rear-mounted engines like a Citation or Phenom? Are those considered centerline thrust since they're so close to it?

I can see the asymmetric thrust situation being an issue on something with wing-slung motors, but it can't be as significant on the tail, right?
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it depends on the jet with the tail mounted engines. Have done a single engine go around with one just at idle thrust for practice in a T-38, and there was next to no asymmetric thrust, but it’s engines are a foot or so off centerline. Had a loss of thrust in an A-10 on takeoff once while heavyweight, a jet which is already underpowered with two 9000 lb/thrust motors for a jet that’s 44,000-50,000 lbs on takeoff. Kept it accelerating a bit on the runway to get a few more knots before rotation, and still had to have some significant rudder and aileron to maintain directional control. Had I rotated earlier, it’s quite possible that there wouldn’t have been enough rudder effectiveness available. The climb rate was slow, but not bad enough to get me to jettison the stores racks underneath and hit the fuel dump, so that was good. But between the two aircraft in similar situations, they handled differently. Although the T-38 doesn’t really have tail mounted engines per se, with it having engines that are inside the fuselage, as well as the two being completely different airframe designs in terms of drag, weight, etc.
 
killbilly said:
Makes sense.

Is there much asymmetric thrust in a biz jet with rear-mounted engines like a Citation or Phenom? Are those considered centerline thrust since they're so close to it?

I can see the asymmetric thrust situation being an issue on something with wing-slung motors, but it can't be as significant on the tail, right?
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Yeah. It's definitely a lot of asymmetric thrust. The Challenger 300 actually has prop like P-factor tendencies. So it takes a touch of right rudder for takeoff and rudder trim adjustments anytime power is adjusted.

Engine failure at V1 requires nearly full rudder. Engine failure after rotation causes quite a bit of roll that needs to be corrected with a good amount of rudder. It also has substantial roll on single engine go around if power and rudder aren't simultaneously applied.
 
killbilly said:
Makes sense.

Is there much asymmetric thrust in a biz jet with rear-mounted engines like a Citation or Phenom? Are those considered centerline thrust since they're so close to it?

I can see the asymmetric thrust situation being an issue on something with wing-slung motors, but it can't be as significant on the tail, right?
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Negative, full or almost full rudder every time in every biz jet I have flown, and that’s quite a few jets.

Now the rudder is obviously going to be smaller then a wing slung airplane, so that’s the trade off.
 
T/O w/FSII said:
Negative, full or almost full rudder every time in every biz jet I have flown, and that’s quite a few jets.

Now the rudder is obviously going to be smaller then a wing slung airplane, so that’s the trade off.
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…vacuum flush toilets and slats… :)
 
killbilly said:
Makes sense.

Is there much asymmetric thrust in a biz jet with rear-mounted engines like a Citation or Phenom? Are those considered centerline thrust since they're so close to it?

I can see the asymmetric thrust situation being an issue on something with wing-slung motors, but it can't be as significant on the tail, right?
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Can’t speak to the smaller businesses jets, but in the CRJ (essentially a large one) there is definitely asymmetric thrust that requires a decent amount of rudder.

It didn’t seem that different from the ATR, probably because the ATR has a ginormous rudder and is maybe a touch underpowered.

Never had engine out training in the ATR-72 (sim was a 42) but I’d bet it would even be easier because of how long that airplane is…the rudder has legit authority.
 
I've been lucky enough never to have a V1 cut in an actual airplane, but if the sims are to be believed, the amount of rudder necessary to keep the airplane on the runway is "most of it", whether you're in a Beechjet or a 747. There's some variation, obviously, but *at or around v1*, they're all pretty similar, AFAICT. Presumably because whatever the amount of rudder authority which is necessary is mandated by certification standards, and there's an obvious countervailing interest in keeping the rudder/stab as small as possible for efficiency purposes. Thus, "most of it", QED, etc etc.

Where things get interesting is at lower speed. In a tail-engine bizjet, it's presumably not a huge big deal if you lose one at low speed, certainly I don't remember ever having trained for it. In a 74, on the other hand, losing one (outboard) engine right after you've spooled all the way up is (reportedly) Mr. Toad's Wild Ride.
 
A lot of tail mounted business jets have a rudder bias system that, when armed, will automatically apply rudder towards the good engine in the case of one engine dropping out. Some are powered by bleed air, functional tests can be fairly involved and lengthy.
 
Lear 45 family has Rudder Boost.

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Boris Badenov said:
I've been lucky enough never to have a V1 cut in an actual airplane, but if the sims are to be believed, the amount of rudder necessary to keep the airplane on the runway is "most of it", whether you're in a Beechjet or a 747. There's some variation, obviously, but *at or around v1*, they're all pretty similar, AFAICT. Presumably because whatever the amount of rudder authority which is necessary is mandated by certification standards, and there's an obvious countervailing interest in keeping the rudder/stab as small as possible for efficiency purposes. Thus, "most of it", QED, etc etc.

Where things get interesting is at lower speed. In a tail-engine bizjet, it's presumably not a huge big deal if you lose one at low speed, certainly I don't remember ever having trained for it. In a 74, on the other hand, losing one (outboard) engine right after you've spooled all the way up is (reportedly) Mr. Toad's Wild Ride.
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There’s a set of tire marks on the beginning of 33L in ICN that seem to tell a story like that.

As for the plane flying on it’s own, I’m not so sure. I’ve done a wind shear departure where you rotate at the highest theoretical VR for thar runway instead of the one that corresponds to your actual weight. The plane felt a little squirrely but it wasn’t like it was trying to jump off the ground.
 
knot4u said:
A lot of tail mounted business jets have a rudder bias system that, when armed, will automatically apply rudder towards the good engine in the case of one engine dropping out. Some are powered by bleed air, functional tests can be fairly involved and lengthy.
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The Challenger 300 does not...which makes it interesting/fun watch Hawker guys go through 300 training from what I hear.
 
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