Piper VS Cessna Accident comparison

[Ted]

Not entirely. If you mean losing control after an engine failure, you're correct. But, let me give you a scenario...

It's 2009. You've gotten your Private ASEL and your instrument rating, and you wanted a twin but you couldn't get insurance on your dream 310 or Aztec until you got 100 multi hours, so you purchased a Seminole to get your AMEL and build time.

Following so far...

You're going on a cross country flight with some friends, loaded to gross with people and fuel. Conditions at IPT are 00000KT OVC006 and 1SM. You take off, and at 600 AGL/1100 MSL you enter the clag, just as you have an engine fail. You already noted, of course, that the takeoff mins and obstacle departure procedure state that you should climb via the ILS localizer front course or PIX NDB to 2500 feet and that you need to maintain a minimum climb gradient of 255'/nm to 1600 feet.

IIRC, the Seminole's Vyse is 88 knots. I don't have the charts handy for performance data at the moment, but you'd probably be lucky to get 100fpm out of the Seminole - Single-engine service ceiling is only 3800 feet, which means the best you could possibly do is 50fpm at 3800, so 100fpm shouldn't be too out of line. At 1.5nm/min, that means your climb gradient after the failure is 67'/nm. Assuming you got to 600' (AGL, 1100' MSL) in one mile with both engines, a fairly reasonable assumption, that puts you below the climb gradient after 2.83 nautical miles, at about 1250 MSL. So far, that's only a loss of the terrain separation required by TERPS, but there's rocks below causing that. The best you can do is to stay on the localizer at Vyse.

It won't be enough. By my calculations, the aircraft wreckage will be found at approximately 2200 MSL on the side of North Mountain.

Ok, I follow so far.

There's a reason for that saying. Twins *may* give you a slightly increased chance in some situations, and in others they're just as bad or worse.

And I've also had people tell me that four wheel drive is "four more ways to get stuck". Comes back to operator error. I'm not sure I see how the scenario you gave me actually has you worse off with the twin than with the single, though. With the single you're still going down, and the landing options if you're taking off of runway 9 aren't great. Just as bad for 12 and 30, worse for 27. I suppose better to hit the ground when you're trying to land than when you're not. However, if you're taking off on runway 9, I'm not sure you'd hit the mountain... last I recall when I was doing touch-and-gos off of 9, it clears the mountain completely if you head in a straight line following the localizer. If you did 12, 27, or 30 it would be a little more questionable, I agree, but if you're following the localizer out, that would put you on a heading of 9. You won't be able to keep up with the climb rate you're supposed to, but it also seems reasonable that you'd be able to get enough altitude to clear other obstacles in the area (which really aren't that high other than the mountain, and I think you'd avoid), pick up the Williamsport VOR, and from there you can work on turning around and then following the ILS back in.

Alternately, you could decide that you can't safely do this, and execute an emergency landing in a straight line.

Obviously this is all speculation, though, since we're just playing out scenarios. I understand that there are reasons for the saying, but there are reasons for every saying. It doesn't mean that any of them are true to all situations, or to all individuals.

FWIW, I used to be a big fan of twins too. I wanted a Baron. I still want a Twin Comanche. But, you have to realize that many twins are gonna leave you in a world of hurt in certain situations. It really wasn't very difficult for me to develop a scenario for you at your home airport like this... That should tell ya something.

Alright, but then I suppose the question I have is how does this actually leave me worse off than a single engine failure? I still see that as coming down to a matter of proper risk management. My point was not to turn this into a single vs. twins thread. I do understand that single engine performance on a lot of twins is pretty rotten, but my point is thinking of one of the planes that I am interested in which has better single engine performance. Also, there's nothing about having a twin that doesn't prevent you from saying "Ok, I lost one engine, I need to pull the other one back and just land."

Either way, I've already looked into the insurance and I can't get insurance on any twin for a while yet (200 hrs minimum), so the point is fairly moot for me.

 

[PittsDriver]

what about my Meridan?

Well, if we're going to burn jet A, what about a Citation X?

 

[PittsDriver]

There's a reason for that saying. Twins *may* give you a slightly increased chance in some situations, and in others they're just as bad or worse.

Actually you bring up a good point that's probably more related to the original thread than the twin vs. single argument. A twin that won't climb well on one engine (or has a low SE ceiling) would seem to me to clearly be accepting greater risk for little or no gain. Thus I would say that a Seminole, your case, is a less safe aircraft than a single engine plane. There's more chance for something to go wrong in this twin and it's not offset by increased safety margin. I personally wouldn't consider owning a twin that didn't climb well on one engine. That issue might have something to do with how few piston twin product lines have survived. I'll still assert that any safety comparisons of piston singles are pretty futile exercises. Once you decide to haul around extra engines for safety, there may be more distinction to be made between types.

You know, another way to slice this would be by equipment. I'll postulate that any HP single sporting XM weather, traffic, & terrain is a much safer bird than any HP single without. If you're looking to make a meaningful safety comparison of planes on a shopping list, I'd start there.

 

[Ghery]

Pipers are better than Cessna's everybody knows that.

With time in both, I'll say that the C-182P is a LOT more comfortable than a 1969 PA-28R-200.

 

[flyingcheesehead]

I'm not sure I see how the scenario you gave me actually has you worse off with the twin than with the single, though. With the single you're still going down, and the landing options if you're taking off of runway 9 aren't great.

Oddly enough, the Single might be better simply because you have no options. Pitch for minimum sink, go down straight ahead until you can see something and hope you have enough visibility and time to land somewhere. I don't think, after having one engine fail, I'd even think about shutting down the other one.

At that point, 1nm from the airport and 600 AGL there's a potentially better option - You're almost up to circling minimums, so you could make a left turn (note the "circling south of runway 9-27 NA" on the plate), probably a 210-degree teardrop, and then let down until you can see the field (hopefully). All of this is predicated on you KNOWING that plate inside and out before takeoff, which, frankly, you probably won't. (I have a return-to-field plate handy when I take off IFR, but I don't go through a full approach briefing. Does anyone else?)

However, if you're taking off on runway 9, I'm not sure you'd hit the mountain... last I recall when I was doing touch-and-gos off of 9, it clears the mountain completely if you head in a straight line following the localizer.

That's assuming the localizer was perfect. The mountain is near the service volume limits of the localizer, so you may be losing usable signal out that far. In addition, you're 18 miles from the runway. The localizer width is 700 feet at the threshold of the runway, so do the math... It's gonna be pretty wide way out there by the mountain. You may miss it, you may not. (If you're lucky, maybe you'll get some upslope lift! ) It certainly protrudes near enough to the localizer that you're required to be at 3700 feet until PIX, and it appears to be the controlling obstacle so it is likely inside the localizer path.

All just an exercise in decision-making and such, though, and making a point that the twin isn't 100% safe. It's been fun, actually, looking things up and doing calculations and running through potential scenarios. I hope you learned as much as I did or more.

 

[Ted]

Oddly enough, the Single might be better simply because you have no options. Pitch for minimum sink, go down straight ahead until you can see something and hope you have enough visibility and time to land somewhere. I don't think, after having one engine fail, I'd even think about shutting down the other one.

That is a good point. Don't give someone any other option and they can't take the option that happens to be more dangerous.

At that point, 1nm from the airport and 600 AGL there's a potentially better option - You're almost up to circling minimums, so you could make a left turn (note the "circling south of runway 9-27 NA" on the plate), probably a 210-degree teardrop, and then let down until you can see the field (hopefully). All of this is predicated on you KNOWING that plate inside and out before takeoff, which, frankly, you probably won't. (I have a return-to-field plate handy when I take off IFR, but I don't go through a full approach briefing. Does anyone else?)

Agreed. It also depends on what exactly your visibility is. In this scenario, with the clouds being at 600' AGL, you could actually probably manage to turn around and land back at the airport. Difficult, certainly, but doable. Of course, you could also screw up, put yourself into a cross-control stall on a single engine and then you're probably on the ground in a firey mess.

That's assuming the localizer was perfect. The mountain is near the service volume limits of the localizer, so you may be losing usable signal out that far. In addition, you're 18 miles from the runway. The localizer width is 700 feet at the threshold of the runway, so do the math... It's gonna be pretty wide way out there by the mountain. You may miss it, you may not. (If you're lucky, maybe you'll get some upslope lift! ) It certainly protrudes near enough to the localizer that you're required to be at 3700 feet until PIX, and it appears to be the controlling obstacle so it is likely inside the localizer path.[/quote[

True, and error has to be accounted for. I will say, on the times I've flown in on the localizer it seems to have been pretty accurate on this particular one, though.

All just an exercise in decision-making and such, though, and making a point that the twin isn't 100% safe. It's been fun, actually, looking things up and doing calculations and running through potential scenarios. I hope you learned as much as I did or more.

Yes, and it's a lot easier to do decision making in front of a computer screen than when it actually happens. Of course, this is how you hopefully prep your mind so that when something goes wrong you know what you're doing and have a higher chance of survival should a problem arise.

When I first flew in a twin (the Aztec), my instructor went over with me before takeoff "Alright, so we need to be ready in case we have an engine failure on take-off" and then went over the points of when we pull the gear up, that when the gear is up that is the go/no go threshold, speeds and conditions for all of these things, etc. That certainly helps, because it means we've already decided this is what we're going to do should something happen.

Obviously twins aren't 100% safe, and I think they have a significnatly higher amount of the safety placed on the judgement and skill of the operator than a single, simply because you have these extra options to screw up. I certainly learned from this exercise, though. Thanks, Kent!

 

[flyingcheesehead]

Agreed. It also depends on what exactly your visibility is. In this scenario, with the clouds being at 600' AGL, you could actually probably manage to turn around and land back at the airport. Difficult, certainly, but doable.

And then the dilemma is... When you do the teardrop, do you climb to avoid obstacles, or try to descend below the 600' ceiling and potentially whack something before you can see? That's a tough one to answer.

True, and error has to be accounted for. I will say, on the times I've flown in on the localizer it seems to have been pretty accurate on this particular one, though.

My point wasn't that the localizer was inherently inaccurate, only that at the range the mountain is, it will be very wide, and right at the limits of the service volume (see AIM 1-1-9 for a picture of the service volume for a localizer).

Yes, and it's a lot easier to do decision making in front of a computer screen than when it actually happens. Of course, this is how you hopefully prep your mind so that when something goes wrong you know what you're doing and have a higher chance of survival should a problem arise.

Bingo!

 

[poadeleted20]

If I've already entered the clag when I lose one engine in a twin at 600 AGL, I am most unlikely to try a turnback unless I'm on fire. I will already have Vyse and a good bit more by that point, and even if I'm above the circling mins, I'm almost certainly well outside the protected zone for circling (see Figure 5-4-23 in AIM Section 5-4-20f) so I have no idea what altitude to which I can safely descend. Therefore, if the airplane is still flying and there's no reason to believe any more problems are imminent, I'll fly the SIAP.

 

[jwriteclub]

I did my instrument training with a retired Air Force Major.

We briefed the take off and take off alternate before every flight.

I usually just brief the take off field when I fly a single, although I make sure to have the plate for an alternate handy.

I have never had to return on an IMC day so far (knock on wood), but when that day comes, hopefully I'll be ready to go right back in.

~ Christopher

 

[flyingcheesehead]

I moved the instrument scenarios to a new thread for further discussion.