ILS Emergencies OEI

[Everskyward]

It's why in any situation you need to take a look at the actual aircraft performance and what your risk tolerance is.

In your case doing mapping, the risk of potentially not being able to fly on one engine if you had an engine failure was part of the job. If it's not a risk you were willing to take for the money offered, then you could have taken a different job.

I didn't see much of a difference in risk because I had done the job for years flying a single.

 

[Ted]

Wally's got it. The reason planes like the 310 and Baron have two engines is because they need two engines to have enough power to produce the desired speed and payload. Back in the day, they just put more cylinders on the engine, until you ended up with something like the An-2. However, the other issues with radial engines made them undesirable for these purposes, and there's just no way to build an air-cooled horizontally-opposed engine that produces more than about 350 HP reliably -- just ask anyone who owned a 400 Commanche or a P-Navajo, with those eight-cylinder IO/TIO-720 engines.

P-Navajos had TIGO-541s on them producing 425 HP. The TIGO-541s did have variants up to 450 HP. You are correct, they weren't very reliable.

So, when you start needing more than 400 HP to get the desired capability, the only way to get it is to put two engines on the plane. Sure, you can go turbine, and have plenty of reserve power, but then the cost factor goes up enormously -- check the price of a TBM-700 versus a piston twin of the same capability, and that's only one turbine engine. That means if you want the capability and the economy, you need two piston engines, and both of them running, or things get ugly fast.

That part is true. But, you can get OEI safety margin out of piston twins if loaded properly, as Bruce can attest. It also depends on what phase of flight your engine fails in. If it fails in cruise, you can be looking at the difference between a forced landing and a landing at the airport of your choice. Trips like my flights over the Gulf of Mexico or in northern Canadian wilderness (at these longitudes) are areas where I don't need much altitude to not hit anything make it easy. Mari had the other end of the spectrum, where anything short of a King Air wouldn't be giving you much of any performance.

 

[Ted]

I didn't see much of a difference in risk because I had done the job for years flying a single.

Exactly. One could argue your negative is you have twice the probability of an engine failure, but I'd say your true risk isn't much different in a percentage.

 

[poadeleted20]

That part is true. But, you can get OEI safety margin out of piston twins if loaded properly, as Bruce can attest.

Agreed, but then you no longer get the payload the plane was designed to haul. As I said, if you want the "book" speed and the payload, you need both engines running. What I should have added was, "or to buy a lot of extra power, like an Aztec to haul a Seminole load."

 

[Everskyward]

Exactly. One could argue your negative is you have twice the probability of an engine failure, but I'd say your true risk isn't much different in a percentage.

True, that would increase the risk, as would the greater energy while hitting the ground. However, two engines would probably decrease the risk if you lost one at altitude because it would give you a better glide ratio and more options.

 

[gismo]

I don't know what you guys are talking about. If you lose an engine you only lose half the power and performance so going around shouldn't be an issue.




; )

Unfortunately the half you lose is the half that provides the climb performance .

 

[dtuuri]

Light twins with one caged around here are just gliders with a better glide ratio over a single with an engine out. Maybe not even better depending on load.

Turbochargers can easily double a light twin's single engine service ceiling. My old Twin Comanche's was 5,000' or 6,000', but the tubo'd ones are up around 19000'.

dtuuri

 

[Ted]

Agreed, but then you no longer get the payload the plane was designed to haul. As I said, if you want the "book" speed and the payload, you need both engines running. What I should have added was, "or to buy a lot of extra power, like an Aztec to haul a Seminole load."

I think we have a habit of looking at things from slightly different perspectives. Extra power is a matter of design requirements. Yes, book speed and payload you'll need two engines. And even with a light payload, you'll need both engines for book speed.

After that, you have a performance question of what your desired performance is. The reality is that gross weight is a function of many factors - desired performance and payload, strength of the airframe, etc.

So now let's say that you redefine your max payload (as Bruce has) to get the performance that you desire. Still plenty legal. You could say that it's excess power that you're buying, personally I'd say you're just increasing your safety margin. You get a plane like a Seminole, and even under gross you're not going to have much of any performance on one engine, other than down.

True, that would increase the risk, as would the greater energy while hitting the ground. However, two engines would probably decrease the risk if you lost one at altitude because it would give you a better glide ratio and more options.

Yep. So in your case, I'd say it averages out to about the same. As an engineer, this guess is certified accurate.

Colorado is tricky flying just because of the altitude. I'll admit to being happier about my flatland flying.

 

[Ted]

Unfortunately the half you lose is the half that provides the climb performance .

Which is where planes like your upgraded Baron and Cloud Nine's upgraded 310 shine.

 

[dtuuri]

P-Navajos had TIGO-541s on them producing 425 HP. The TIGO-541s did have variants up to 450 HP. You are correct, they weren't very reliable.

I actually helped crew one for a year back in 1975/76 for EJA, but other than a manufacturer's defect in the camshafts at 700 hours, both engines went to TBO (1200 hrs). In that time, I found one broken exhaust pipe on preflight. Heck, the C-421 exhaust system looks like it was built broke by comparison.

It's no rocket on one engine though. I'd like to think that was due to improper simulated thrust during training. When I told the chief pilot a 421 had 25% (??) more SE climb ability, he says, "So what, 125% of nothing is still nothing." Good point.

dtuuri

 

[poadeleted20]

I think we have a habit of looking at things from slightly different perspectives. Extra power is a matter of design requirements. Yes, book speed and payload you'll need two engines. And even with a light payload, you'll need both engines for book speed.

After that, you have a performance question of what your desired performance is. The reality is that gross weight is a function of many factors - desired performance and payload, strength of the airframe, etc.

So now let's say that you redefine your max payload (as Bruce has) to get the performance that you desire. Still plenty legal. You could say that it's excess power that you're buying, personally I'd say you're just increasing your safety margin. You get a plane like a Seminole, and even under gross you're not going to have much of any performance on one engine, other than down.

I think we're on the same page here, just saying it different ways.

 

[Everskyward]

Colorado is tricky flying just because of the altitude. I'll admit to being happier about my flatland flying.

I think it's all in what you have grown to consider normal. When I think about it, all the twins I have flown, from small piston twins and up, have been based in Colorado. I learned at sea level in California and I flew in Missouri for a few years but those were all singles.

 

[Ted]

I actually helped crew one for a year back in 1975/76 for EJA, but other than a manufacturer's defect in the camshafts at 700 hours, both engines went to TBO (1200 hrs). In that time, I found one broken exhaust pipe on preflight. Heck, the C-421 exhaust system looks like it was built broke by comparison.

As with the 421s, a lot of it had to do with how the engines were operated. If you wanted to go for the book speed numbers, they'd be very poor performers. The gearing also did provide some negatives, but could be dealt with easily enough.

It's no rocket on one engine though. I'd like to think that was due to improper simulated thrust during training. When I told the chief pilot a 421 had 25% (??) more SE climb ability, he says, "So what, 125% of nothing is still nothing." Good point.

dtuuri

I always felt the P-Navajo was underpowered (hence why they built the Cheyenne), and the 421 was underpowered (see: Conquest). The P-Navajo engines belonged in the Duke, and then it might've had decent performance. The 421 engines should have been in the 340. In both cases, you'd end up with a plane that had better single engine performance.

 

[Ted]

I think it's all in what you have grown to consider normal. When I think about it, all the twins I have flown, from small piston twins and up, have been based in Colorado. I learned at sea level in California and I flew in Missouri for a few years but those were all singles.

Very true. Having learned in the flatlands, a twin typically represented improved safety, since our OEI service ceilings don't need to be too high to miss the hard stuff.

 

[Henning]

I'm curious if anyone here has stories to share regarding OEI on an ILS or other vertical guidance approach. I'm not instrument rated, but single-engine go-arounds/missed-approaches don't sound too terribly fun.

If you're in an emergency (OEI, or others if relevant), on an ILS with a low ceiling, would you bust minimums rather than risk being unable to go missed? Treat your minimum altitude as much higher than published just so the fudge-factor altitude is available in a single engine climb-out?

I made a foolish decision to depart out of Hayward into low IMC, lower than the LDA would allow for getting back in, but it was above Oakland's minimums when I got briefed. About 1600' I notice the oil pressure gauge on the left twitching a bit, looked out and saw oil streaming. I caged it and called Bay approach told them I was down an engine and wanted the ILS 11 into Oakland. He read me the approach and got me lined up for the localizer and reported to me "be aware OAK is now reporting below minimums for the ILS", "Thanks for the report, I'm below minimums too, good thing it's a big runway" "Understood, good luck".
Shot it down and broke out at 90' right where I'd expect with the needles in the donut, nice that it works.

 

[bobmrg]

I think highly of the article even if a few details are technically suspect. I understand you've published some good words on the subject too.

dtuuri

I had a lot of help from pilots whose attainments I will never equal..Les Berven, John Deakin, Mike Busch among others, plus advice from the Small Aircraft Directorate.

Bob

 

[bbchien]

Light twins with one caged around here are just gliders with a better glide ratio over a single with an engine out. Maybe not even better depending on load.

Well, Nate, I think you'd choose the turbocharged light twin, 200 undergross over DBL with one feathered, over the piston single at DBL with total power loss. I will be making a runway.

As I say repetitively, it's about load.

If you have a large family, A Seneca is not a true 4 place twin. It can carry 1300 total and be 200 under; that's 750 in the cabin and 4 hours' fuel + 30 min reserve.

You need a Navajo or a C310 (and even then.....the C310 can be fuel limited, to say 200 under), or an Aztec. A T310R 200 undergross does very well on one (provided it doesn't have boots- another thing the marketing department glosses over a bit).

You can forget about the Baron for families of 4 with 200 pound persons. Barons are about "go fast" with two turning. Here's an example of the marketing department reigning supreme.....Eking out a go around from 50 feet, a gross, on a hot day in a Baron is a eyeball peeling experience. I managed it....but I'm not eager to do it again. It too needs to be 200 or so undergross, and then it too is fuel limited.

What I see commonly, and shake my head about, is the owner who packs it full and departs from 3,500 feet successfully and says, "what's the problem?". He SO NEEDS to be reminded of how miserable his Baron is at gross. BT recently.

 

[Captain]

Over DBL with an engine failed and feather I'd abandon ASE and head to RIL. Did ya know RIL is a lower field elevation than BJC?

 

[bbchien]

Yup. Nice broad valley, nice long runway. But it depends. Weather is totally local in the wintertime.....and love that overrun at the west end (not), which if you need in a PA34 you have another problem alltogether.....

 

[aterpster]

Yup. Nice broad valley, nice long runway. But it depends. Weather is totally local in the wintertime.....and love that overrun at the west end (not), which if you need in a PA34 you have another problem alltogether.....

The recommended calm wind runway is 8. Trouble is, its IAPs for the ordinary folks are awful.

But, for the qualified biz jets the RNP Z to Runway 8 is awesome.

 

[bbchien]

The recommended calm wind runway is 8. Trouble is, its IAPs for the ordinary folks are awful.

But, for the qualified biz jets the RNP Z to Runway 8 is awesome.

Yeah

 

[Captain]

EGE is always an option. If RIL and EGE were crap it'd be GJT or the front range (BJC or APA). And if that won't cut it then screw it, we're headin to DEN!

 

[denverpilot]

Well, Nate, I think you'd choose the turbocharged light twin, 200 undergross over DBL with one feathered, over the piston single at DBL with total power loss. I will be making a runway.

I wouldn't, but not for the reason you think.

I don't have the qualifications or the built in survival tactics to fly a light twin.

With a rating, I agree with you.

A man's got to know his limitations.