Great discussion.

John,

if you’ll indulge me and as energy management is sort of the topic, some outstanding pilot work at Bankstown…

https://www.abc.net.au/news/2024-05-...e=abc_news_web

Definitely that which one prefers to observe, rather than experience. Close call, that one.

Trust life continues to treat you well, good sir.

Suggesting it might be preferable to have a lower V1 from a strategic view isn't automatically associated with a reluctance to carry out an RTO from a higher V1. There could be operational reasons one might prefer to favour continuing from a lower V1.

Thanks big pistons forever for you comments and advice. I have to bow to your superior knowledge of the FARs and am not sure how 121 applies to Air Tanker Ops (maybe as guiding principles). However, dropping the load just after an engine failure is not the considered as the preferred option. If the performance considerations have been accurately and correctly considered and applied to the take off, dropping the load should not be necessary following an engine failure. However, in those circumstances it is considered sensible and is the approved procedure to at least consider the dropping the load.

I sense that an unusual perception of risk is influencing performance selection.
Past safety initiatives have focused on the hazards of RTOs from higher speeds.
Whilst statistically there could be concern, it does not follow that these accidents are related to the performance aspects of engine failure.
Data suggests that the likelihood of an engine failure is low in comparison with other issues, and those engine failures which have contributed to accidents occurred after rejecting above V1.

Furthermore, much of the 'go minded' mantra plays-down engine failure and performance issues - see briefing note:

https://skybrary.aero/sites/default/...kshelf/197.pdf

whereas,

"… transport aircraft in Performance Category ‘A’ should be able to safely reject the take off if the decision to do so is made at a speed not greater than the correctly calculated decision speed (V1)."

https://skybrary.aero/articles/rejected-take

For engine failure at any speed below V1, a 'go mindset' has no place in our thinking - its mental clutter, which encourages an incorrect response.

Thanks for your continued contributions Safetypee, you are clearly a well informed Professional and a credit to the aviation industry. The articles that you posted links to are well worthy of reading, thank you for sharing them with us

RM, reverting to the question; the 146/RJ has a good range of performance options with a choice of 3 takeoff flap settings. Choose the lowest V1 according to field length / obstacle limitations.

Some RJs had an optional modification ($$) enabling 33 flap take off, with lower speeds, higher weight. This might only apply to the RJ 100, and specifically considered the old, shorter LCY.

I strongly urge avoidance of exotic fixes for issues perceived as increased risk or a good idea; more often change creates problems. Heed Chesterton' Fence - https://fs.blog/chestertons-fence/

The dump suggestion - not required for certificated performance; in addition to proof of reliability, enquiries might question if it was tested in all take-off configurations.
Similarly avoid the DER process; some very bad - downright dangerous experiences.
More formal certification routes could open a can of worms; was Vmcg reassessed for the 'fat' tanker. I recall removing the baffle across the gear bay - reduced wt, had interesting lateral/directional qualities, thus any changes around the gear doors might influence side force.

As for the RTO hazard, with fading memory there were few, if any engine failures in the high speed portion of take off. Alternatively tyre failures at high speed, inappropriate RTO and overrun, are recalled.

The incident @ page 15 https://skybrary.aero/sites/default/...shelf/1326.pdf involved a RJ, a challenging situation; that Capt also said that if it happened again on a short runway he would continue the takeoff - such is experience.

The last tanker I flew was the Electra. It has been awhile since I flew the airplane and as I recall Loaded V1 to Vr was I think 5 knots, empty it was over 20 kts so dumping the load would definitely give you more options. Also a load of water was deliberately dropped during a takeoff run as part of the initial certification flight testing and it was a non event

I think adding this to your first post would have helped the discussion. I would agree with big pistons. I'm sure you should be able to get credit for dumping at least half the load, and use that TOGW for V1. That is definitely a very narrow use case not defined in the regular ops regulations.

As indicated earlier, the problem lies with certification reliability. It would take lots of money to show that role equipment fuel dumping was OK

Somewhat late to this thread and given the knowledge of several of the contributors, not likely to add much to it, but on a limiting runway, you are almost certainly going to reduce your TOPL by reducing V1. Also, if the aircraft is operated and maintained properly, it shouldn’t have any problem stopping from a V1 derived from the AFM data any more than it shouldn’t with a V1 failure and continued flight. If you want to add a safety margin, reduce the TOW below the TOPL and go full power; if you believe the numbers run with the original performance? As others have said, you are proposing trading a limiting RTO for a limiting EFATO, while reducing the effective payload, which although possible, doesn’t seem to make complete sense?

The software we use can optionally give a V1 range but Company policy is to produce just a single one, so it has been set up that way (highest V1).

This...
Certification is intentionally done with conservatism - e.g. stopping and V1 reject speeds are based on not using the Thrust Reversers, because T/Rs can be MEL'd, and if the V1 reject is due to an engine failure, that T/R is useless.
Having positive margin in an emergency is always a good thing - while having negative margin can turn an emergency into a catastrophe.

V1 = Vr must be nice (no 'dead man's zone'), but when the two speeds are not the same, I thought V1 was the speed at which you have enough runway to stop in but not enough speed to fly - however many engines are running? I was always under the impression that V2/positive rate of climb is the point at which you could execute a safe return even with an engine out? But I'm not a pilot, only a reasonably well-informed enthusiast.

When V1 = Vr, it’s pretty simple. When V1 is less than Vr, if the decision is to go, you must accelerate with the inoperative to Vr and V2. In the C-5, we’d do a rotate increase to improve the OEI climb gradient of up to 15 knots. Sometimes 20 knots between the V1 and rotate, a long time at 150 knots or so. The 727 nearly always operated where V1=Vr, as did the Global Express. It’s not a dead man’s zone, just a segment of the take-off where you’re committed to continue. Often, the numbers can be tweaked to eliminate the split numbers.

Yes, V2 is take-off safety speed where a Part 25 has a specified climb gradient, accounting for any obstacles to return or continue.

You open a number of considerations, in particular are you considering heavy aircraft, commuter, or light twins. The rules, both for design/certification and operation differ with the class of aircraft.

V1 = Vr must be nice (no 'dead man's zone'), but when the two speeds are not the same, I thought V1 was the speed at which you have enough runway to stop in but not enough speed to fly - however many engines are running?

The idea of these speeds is a bit conceptual but it's stood the reasonable test of time. Without too much of a pad available, below V1, with a failure, you should be able to stop. Similarly, above V1, you should be able to go. That's a bit idealistic, and there are a few ifs and buts in the wings but it more or less works pretty well most of the time. There's no guarantees with this stuff, only probabilities and if you push the presumed boundaries what fat there is can rapidly disappear and the folk can end up in a world of hurt.

The certification process tries to balance a bit of conservatism with a bit of commercial practicality with the aim (hope ?) that folks get it all together on the day. Hence the emphasis on over training so that the pilot doesn't have to waste time with cognitive effort directed toward the basic mechanics of doing the exercise on the day.

I was always under the impression that V2/positive rate of climb is the point at which you could execute a safe return even with an engine out?

V2 is geared to the situation where you do have a V1 failure. The need, then, is to make sure that you fly the aircraft in a manner that, with all engines going, you make a flightpath which is within the engine out flight path.

So, with a V1 failure, for the Flight Manual numbers, when you get to V2 you should be well-placed to recover the aircraft. The gear is addressed within the segmented takeoff sequence. If you didn't have a failure (the normal situation) it all becomes a bit of a doddle and much easier than with the engine failure.

But I'm not a pilot, only a reasonably well-informed enthusiast.

That's fine. We all try to be well-informed enthusiasts. Some of us fly aeroplanes as well.

I see my good colleague, GF, beat me to the punch. Just to clarify one of his observations. We don't set out to increase the actual speed if we have a failure. If the failure is at the Flight Manual V1 point, you should end up at very close to V2 when you get to 35 ft, providing you fly the aeroplane like the OEM says you should. Obviously, most of the time we don't have a failure and, if we do, it usually is not at V1. So, if we have a failure a bit after V1, we have the benefit of the all engine acceleration up to the failure point with the result that we end up at 35 ft with a speed a bit above V2. Post the O'Hare DC10 mishap, the idea is that, when we get to 35ft, with a failure, if we are

(a) below V2, then increase to, and maintain, V2

(b) at V2, maintain V2

(c) between V2 and, usually, V2+20, maintain the speed you have

(d) above V2+20, pitch up to reduce to V2+20

The reason we don't accelerate to increase the climb speed (and get a bit better climb rate) is that, while accelerating, we are likely to end up in the rocky bits which is not a good life options strategy.