V1 in small twins

[AuxBatOn]

From the Piper Seminole POH, Emergency Procedures , Engine Failure After Takeoff

“In certain combinations of aircraft weight, configuration, ambient conditions and speed, negative climb performance may result. Refer to One Engine Inoperative Climb Performance chart,”

I am with Pelmet. Procedures for large aircraft which have demonstrated capabilities to continue a takeoff after an engine failure should not be extrapolated to small piston twins

Aux. How much experience do you have flying light piston twins ?

I have some but probably not as much as you guys. The experience I have however was largely focused on demonstrating certification requirements for exactly this. I do have a fair amount of experience in twins certified under part 23 but above 6,000 lbs/turbo-props.

Like I said before, I do not exclude the possibility of putting it down after becoming airborne. But there may not be runway in front to safely land on. And again, it comes down to knowing the aircraft you fly and having mental gates on actions to be carried out in case of emergency. That was the point I was trying to make before the noise started.

Pelmet: here’s the FAR I was referring to:

Sec. 23.67 — Climb: One engine inoperative.

(a) For normal, utility, and acrobatic category reciprocating engine-powered airplanes of 6,000 pounds or less maximum weight, the following apply:
(1) Except for those airplanes that meet the requirements prescribed in §23.562(d), each airplane with a VSOof more than 61 knots must be able to maintain a steady climb gradient of at least 1.5 percent at a pressure altitude of 5,000 feet with the—

(i) Critical engine inoperative and its propeller in the minimum drag position;

(ii) Remaining engine(s) at not more than maximum continuous power;

(iii) Landing gear retracted;

(iv) Wing flaps retracted; and

(v) Climb speed not less than 1.2 VS1.

For a stall speed of less than 61 kts, the climb/descent gradient just needs to be determined (no minimum climb gradient).

23.562 is, I think, related to safety occupant.

[Big Pistons Forever]

But there may not be runway in front to safely land on. And again, it comes down to knowing the aircraft you fly and having mental gates on actions to be carried out in case of emergency.

I guess we are going to have to agree to disagree on this because I am coming at it from a completely different perspective

The first perspective is that for that relatively brief period between just after lift off to gear up and better than VYse, if the engine fails my decision isn’t predicated on whether or not I can “safely landing on the remaining runway”, it is to not injure myself or anyone else. The insurance company just bought the airplane and so I don’t care what it looks like when it comes to a stop. The accident record shows EFATO’s in single engine airplanes almost always end well if the aircraft is flown under control to the ground. Closing the throttles means all attention can be devoted to flying the aircraft in a very high stress and time limited situation.
Light twins will glide and stall at similar speeds to singles so I think the comparison is very valid

The second perspective is the idea of having situationally dependent “mental gates”
Large aircraft SOP’s have steadily simplified the decision making in this scenario because human factors research show that even very experienced pilots often don’t make good decisions in this scenario, so the idea that light pilots will do better than transport pilots doesn’t resonate with me and is sadly not supported by the accident rate.

2500 hrs PIC on Pa 23/30/31/34/44/60 Cessna 310/340/421, Beech Baron 55 and BN Islander

[AuxBatOn]

But there may not be runway in front to safely land on. And again, it comes down to knowing the aircraft you fly and having mental gates on actions to be carried out in case of emergency.

I guess we are going to have to agree to disagree on this because I am coming at it from a completely different perspective

The first perspective is that for that relatively brief period between just after lift off to gear up and better than VYse, if the engine fails my decision isn’t predicated on whether or not I can “safely landing on the remaining runway”, it is to not injure myself or anyone else. The insurance company just bought the airplane and so I don’t care what it looks like when it comes to a stop. The accident record shows EFATO’s in single engine airplanes almost always end well if the aircraft is flown under control to the ground. Closing the throttles means all attention can be devoted to flying the aircraft in a very high stress and time limited situation.
Light twins will glide and stall at similar speeds to singles so I think the comparison is very valid

The second perspective is the idea of having situationally dependent “mental gates”
Large aircraft SOP’s have steadily simplified the decision making in this scenario because human factors research show that even very experienced pilots often don’t make good decisions in this scenario, so the idea that light pilots will do better than transport pilots doesn’t resonate with me and is sadly not supported by the accident rate.

2500 hrs PIC on Pa 23/30/31/34/44/60 Cessna 310/340/421, Beech Baron 55 and BN Islander

You out-experience me on that type of flying for sure. My perspective is indeed different - I tend to trust the books and base my actions on this (and that makes sense from my background) For the record, safely in a situation like this is not injuring or killing myself or others. I don’t care about metal at that point.

The mental gates work well for me (and I had to apply them on takeoff on three occasions). Perhaps it doesn’t work well for others.

I did a bit of a survey on Youtube of Barons taking off. All of them (15 or so), except one (but that is debatable) raised the gear well below a safe climbing speed (sometimes as soon as lift off!), even with runway to spare. It doesn’t prove anything but that most pilots will accept impairing one of their options early on.

[telex]

This is why no V1 speed is promulgated for light twins because a V1 speed by definition requires that the aircraft can continue the takeoff after an engine failure at or above V1.

Thread title is V1 in small twins.

Apparently there is no V1 in small twins.

[pelmet]

From the Piper Seminole POH, Emergency Procedures , Engine Failure After Takeoff

“In certain combinations of aircraft weight, configuration, ambient conditions and speed, negative climb performance may result. Refer to One Engine Inoperative Climb Performance chart,”

I am with Pelmet. Procedures for large aircraft which have demonstrated capabilities to continue a takeoff after an engine failure should not be extrapolated to small piston twins

Aux. How much experience do you have flying light piston twins ?

I have some but probably not as much as you guys. The experience I have however was largely focused on demonstrating certification requirements for exactly this. I do have a fair amount of experience in twins certified under part 23 but above 6,000 lbs/turbo-props.

Like I said before, I do not exclude the possibility of putting it down after becoming airborne. But there may not be runway in front to safely land on. And again, it comes down to knowing the aircraft you fly and having mental gates on actions to be carried out in case of emergency. That was the point I was trying to make before the noise started.

Pelmet: here’s the FAR I was referring to:

Sec. 23.67 — Climb: One engine inoperative.

(a) For normal, utility, and acrobatic category reciprocating engine-powered airplanes of 6,000 pounds or less maximum weight, the following apply:
(1) Except for those airplanes that meet the requirements prescribed in §23.562(d), each airplane with a VSOof more than 61 knots must be able to maintain a steady climb gradient of at least 1.5 percent at a pressure altitude of 5,000 feet with the—

(i) Critical engine inoperative and its propeller in the minimum drag position;

(ii) Remaining engine(s) at not more than maximum continuous power;

(iii) Landing gear retracted;

(iv) Wing flaps retracted; and

(v) Climb speed not less than 1.2 VS1.

For a stall speed of less than 61 kts, the climb/descent gradient just needs to be determined (no minimum climb gradient).

23.562 is, I think, related to safety occupant.

The most important sentence in your quote is.......

"For a stall speed of less than 61 kts, the climb/descent gradient just needs to be determined (no minimum climb gradient)". This covers a lot of light twins, and is why a lot of manufacturers target a maximum 61 knot stall speed.

Be prepared to close the throttles and land on whatever terrain is ahead after an engine failure shortly after getting airborne. Remember, prepared doesn't mean you will do it, just be prepared to do it based on how things are going. I suspect it is a lot easier to say than to do.

[AuxBatOn]

The most important sentence in your quote is.......

"For a stall speed of less than 61 kts, the climb/descent gradient just needs to be determined (no minimum climb gradient)". This covers a lot of light twins, and is why a lot of manufacturers target a maximum 61 knot stall speed.

Be prepared to close the throttles and land on whatever terrain is ahead after an engine failure shortly after getting airborne. Remember, prepared doesn't mean you will do it, just be prepared to do it based on how things are going. I suspect it is a lot easier to say than to do.

It wasn’t in my quote but it is in the next FAR item.

I would argue that a lot of light twins have a Vso of more than 61 kts. The other part is that the aircraft may still be capable of climbing on one engine (even at MTOW), despite the certification requirements.

As I have said at least twice now: know your aircraft, know what it can do in the current conditions. Having the “close the throttle and land straight ahead every time” mentality is no better than having the “keep flying every single time” mentality.

FWIW, the examples that were brought up were about a Navajo and a King Air 90. This is where my initial comments regarding certification and performance came from: they have certification requirements (positive single engine climb gradient)

[Maynard]

Most, if not all, operators that fly twin engine aircraft, use V1 as the decision speed for small twins. An engine blows up before V1, you abort, an engine blows up after V1, you continue and rotate. Ok, great.

Now, V1 makes a lot of sense if you look at airline operations. It truly is a decision speed. Reduced power take offs, runway conditions etc are all taken into account to be able to say with a certain degree of precision that if you try to abort above V1, you'll slide off the end of the runway. If you continue single engine before V1, you'll hit someting at the end of the runway. This makes sense. V1 has value. You can trust it. It's well defined.

Looking at smaller operators flying twins, they also use V1. For small jets, for twin turbines, even for piston twins. I find the values and meaning of those V1 speeds often pretty useless, and in a way pretty detrimental to safety.

Let's start with an example of a navajo. Accelerate stop somewhere around 3000 ft, single engine stake off distance probably around the same. This airplane is now taking off from a 10000 ft runway, with a V1 calculated for a 3000 ft runway. You have 7000 ft of extra runway that is not taken into account. Let's say its engine catches fire past v1, would it not be much safer to just abort in the remaining extra 7000 ft? On such runways, why would V1 ever be lower than Vr?

Same for a king air class kind of airplane. They are great performers. Why treat V1 as a life and death decision on a long runway? If you have 10 000 ft and something happens, even past v1, why not abort?

It just drives me bonkers. Discussing it with management or training pilots, even crew members always results in "But it's V1, it's the decision speed, you can't abort past V1!".

Thoughts? Am I missing something?

This is where the difference comes in from the "checklist only" type of pilots vs the common sense pilots. It shouldn't even be a deep thought if you're flying a small twin from a long ass runway, screw V1; with 5000 in front put the thing back down. V1and VR will be within a few knots so you're likely airborne with 6-7000' left....even at 2-400' AGL you could get it back down and stopped before the end

[pelmet]

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[AuxBatOn]

That is not from the FAR, this was my own comment.

[photofly]

He didn’t say it was from the FAR.

[pelmet]

That is not from the FAR, this was my own comment.

I would strongly recommend using quotation marks when making posts with quotes from FAR's combined with your own remarks, especially when not changing the spacing as it can lead to great confusion(Or perhaps some other method of highlight). Either way, my point remains the same....."For a stall speed of less than 61 kts, the climb/descent gradient just needs to be determined (no minimum climb gradient)" is still the most important part of what you posted at the time and states exactly what I had posted earlier as seen here with the important part in bold....

viewtopic.php?p=1133822#p1133822

However, the point has been made about your focus on King Air type aircraft, so I will provide another post soon on that.

[pelmet]

As I have said at least twice now: know your aircraft, know what it can do in the current conditions. Having the “close the throttle and land straight ahead every time” mentality is no better than having the “keep flying every single time” mentality.

I certainly never said that. I said.....

Be prepared to close the throttles and land on whatever terrain is ahead after an engine failure shortly after getting airborne. Remember, prepared doesn't mean you will do it, just be prepared to do it based on how things are going. I suspect it is a lot easier to say than to do.

[pelmet]

I provided a link to this report in an earlier post.....

"As discussed in Section 1.20.2, there was no requirement for most multi-engine aircraft below 5,700 kg maximum take-off weight (MTOW) to demonstrate a one-engine inoperative climb capability from takeoff. As a result, there was a need for pilots to follow procedures for managing an engine failure if it occurred late in the take-off roll, or prior to the nominated one-engine inoperative climb speed being achieved.

The aircraft manufacturer’s Pilot’s Operating Manual for LQH stated that the ‘decision speed’ was 100 kts. The manufacturer specified the decision speed in relation to accelerate stop performance (see Section 1.20.6).The term ‘decision speed’ was not defined in the manual. However, the term is generally regarded as being the speed at or above which, should an engine fail, the takeoff would be continued.

Some operators of this category of aircraft use a decision point rather than a decision speed. A decision point is usually a combination of speed with one or more additional parameters such as a height above ground level, a positive rate of climb and/or a configuration (for example, gear
retracted). Given the limitations of one-engine inoperative climb performance, it is a commonly recommended practice that the speed parameter of the decision point should be at or above Vyse.

Depending on the operator’s procedures, the decision point for a particular flight may vary depending on ambient conditions, runway characteristics, surrounding terrain and aircraft weight. For example, during a takeoff on a long runway the decision point may occur further along the aircraft flight path relative to a takeoff on a shorter runway.

Figure 17 shows the relationship between liftoff, a ‘reject take off area’, a decision point and a ‘continue takeoff area’. The ‘reject takeoff area’ is where the aircraft may not perform adequately on one engine, even if it is correctly configured. After the decision point, in the ‘continue takeoff
area’, the aircraft will probably be able to perform adequately on one engine when correctly configured, Depending on the subsequent aircraft performance, the pilot may need to reassess the decision to continue the takeoff with one-engine inoperative. Figure 17 shows the decision point as occurring at Vyse and the landing gear retracted or in transit to the retracted position; this is illustrating a commonly recommended practice and may not be appropriate for all situations."

Bottom line, if you choose to operate into airstrips with aircraft like this where you don't have sufficient accelerate-stop distance using a reject point soon after getting airborne, you are in a gray area that gets larger and larger as density altitude and weight increase.

[cncpc]

Personally I use gear selected up and blue line plus 5kts as decision gate. Below that if the engine fails the automatic response is to pull back both throttles and I will take my lumps straight ahead. After that I have the option to identify and feather and continue

Agree with that as far as piston twins go. Not sure what type of aircraft you fly. As for the "After that..." bit, what determines whether you exercise the option? Runway ahead, ability to fly out and come back, uncertainty as to why one failed, and whether the second may only be seconds away...? Or aircraft type and gross weight?

Certainly agree that deciding to take lumps straight ahead can be a lifesaver. No Vmc roll with both pulled back.

As an example, straight Navajo couple hundred of pounds under max at BPFs scenario above, and questionable runway remaining, I'd go. Not a chance in a Chieftain.

I don't agree that in every scenario, you should try and fly away on one with sufficient runway remaining. You've had an engine failure. You've got to get it down under control on a landing area. Unless I'm missing something, you've made a serious error in judgment if you don't take the landing ahead in preference for an opportunity to demonstrate what an ace you are and bang around some sort of circuit to land on the same friggin' runway that was available right in front of you when the engine calved.

[youhavecontrol]

I flew 400 hours on a Seminole and if I remember correctly, it wasn't a speed we were concerned with, but the position of the landing gear. If the gear was down, we would cut power and land straight ahead. If the gear was up, we would continue a shallow climb and initiate the engine failure procedure. Most of the time we had a ton of runway to spare and I'd rather risk a runway excursion than try climbing on one engine in that thing.

[goingnowherefast]

Navajo take-off on a 3500' runway can usually accelerate to Vr and stop. 3500' runway with a 500' clearway, engine fails at Vr + 5 seconds with the take-off continued will fly into the trees at the end of the clearway. The gear is down or in transit with take-off flap, even if it feathers it's self, will be 0 climb or slowly descending. The rejected take-off will over run the runway and come to stop in the swamp before the trees.

The "Vgo" isn't so much a speed, but a gate I'd define as above the tree altitude with the gear retracted. Vstop will be Vr or slightly less. There is a window between rotation and about 100' agl where the Navajo on a 3500' strip won't make it.

Gear up, flaps up, prop feathered at blue line a Navajo will fly one engine above 5000', therefor it meets certification requirements. Trying to outclimb the obstacles after take-off with the gear retracting and t/o flap won't happen, nor does it need to for certification or operation under 703.

[tsgarp]

Aircraft certified in the Commuter and Transport category have to have the ability to loose an engine at/after V1 and still climb away. Aircraft in the Normal and Utility category do not.

The best thing you can do is look at the emergency procedures and performance data in your POH. For most light piston twins (Seneca, Seminole, Aztec, Duchess) the drill for an engine failure before rotation is to close the throttles and apply the brakes. Also, if the aircraft does not have a V1 chart and/or lacks accelerate go data, then the manufacturer never tested its ability to loose an engine prior to rotation and continue the T/O run. This means that should you loose an engine prior to rotation, and elect to keep going, there is no guarantee that you would get airborne or be able to climb away. If you continue the T/O under these conditions you risk going off the end of the runway at high speed or striking the ground in an out of control fashion (stall, spin). If, on the other hand, you close the throttles you risk going off the end of the runway at low speed in a somewhat controlled fashion (assuming you haven’t been really foolish with your accelerate stop distance).

If, on the other hand the POH lists an emergency procedure for engine failure after V1 and contains accelerate-go data and a V1 chart, then the manufacturer has tested the aircraft for it and you are good to go.

[Alex335]

I’m not aware of any light piston twins that have a V1 speed. V1 would imply you are below Vr so still on the ground. Most light piston twins will have a climb rate in the 300fpm range with prop feathered and drag cleaned up. So with the gear down and prop still windmilling the climb rate will likely be negative so continuing will be impossible.

[airway]

Here is what the Seneca POH says. I think it is the Seneca I

engine fail.jpg (125.5 KiB) Viewed 847 times

[Big Pistons Forever]

I’m not aware of any light piston twins that have a V1 speed. V1 would imply you are below Vr so still on the ground.

I think everyone realizes that and instead the term V1 in the context of the "small twins" being discussed is being used as proxy for the point where it would be possible to continue the takeoff after an engine fails. Unlike a true V1 which is a defined speed I would suggest that the "decision speed" is really a decision point for these aircraft and includes not only speed but altitude, aircraft configuration, remaining runway, and departure path obstacles, which makes this a very demanding decision and one which IMO is often not givien the care it deserves.

I would also suggest that that many pilots have a unreasonable level of optimism about how much performance they can actually get out of the airplane after an EFATO