private aircraft question: 1 engine or 2?

In My Humble Opinion
21

No irritation here. You make all good points Gus. All good. And no need for sucking; you’ve seen and done a thousand things I’ve never done. And lived to tell the tale, which speaks volumes about your skill, luck, and brass 'nads. Believe me when I say I respect that; I respect it a lot.

As you say, it all comes down to “How safe is safe enough and for how many dollars?”

The fact that hobbyist GA is dying on the vine is, IMO, a combination of prices going almost straight up, middle class disposable income sliding down, and everyone’s expectations of safety and sophistication going up as well.

What was plenty good enough in 1965 or 1975 isn’t viewed the same nowadays. Even if neither the sky nor the typical factory GA aircraft has changed a bit in that 40-50 years.
It’s a real pity the FAA & the manufacturers and the lawyers and the public have painted themselves into that corner. I have no clue how we’re going to get back out. Which is IMO pretty much necessary if we’re to still have an air travel industry in 40 years when the current crop of pilots dies off.
On a happier note I had lunch today under about 1 mile final of a local GA airport. Lots of bizjets, but then an RV-4 came by with half flaps and 15 degrees of crab into the tropical crosswind. Looked & sounded good.

22

Only if these 2 requirements are met:
1 – the aircraft can climb on 1 engine
2 – the pilot can handle an engine failure.

In the event of an engine failure on takeoff in a conventional twin (one engine on each wing) the aircraft will be yanked silly-ass sideways until the pilot properly feathers the prop and corrects for adverse yaw from differential power. It must happen quickly.

No. If the combined horsepower is the same between a 2 engine plane and a single engine plane the additional drag from conventional twin engine aircraft will create more drag and make it slower.

23

Cessna 172 prices vs. U.S. Median Wage chart

The FAA has been making regulations for almost 60 years, the Civil Aeronautics Authority was making regulations for 20 years before that, and the Air Commerce Act was passed in 1926. I find it hard to believe that regulations have been killing aviation, when aviation adapted to new regs for almost a century.

Similarly, aircraft manufacturers have been dealing with lawsuits all along, and the General Aviation Revitalization Act of 1994 relieved them of some liability. How many airplanes are there less than 18 years old nowadays? Granted, ignorant juries and greedy lawyers resulted in unwarranted awards; but airplane makers still made airplanes and paid the premiums for decades.

The public? There’s a huge problem. When the airplane makers stopped making piston-singles for 11 years, and going forward, things like cell phones, video games, the Internet, ATVs, and a host of other things that take up people’s time and don’t cost as much as flying, basically made people forget about (real) airplanes. Not to mention the enormous shift in wealth from the middle class to the upper class that left potential airplane buyers unable to afford the aircraft for which they were the target market.

When the hiatus struck, used airplane prices went up. But they were still a lot cheaper than new ones after the hiatus ended. With lower sales, there was lower production. Now each airplane cost more to make because of the loss of economies of scale. Since new airplanes are more expensive, buyers tend to buy used airplanes… which makes new ones more expensive. Airplanes are very well built, and airplane makers are competing against their own products. In the olden days ('60s and '70s) people would put 5,000 hours on an airframe, rebuilding the engine once, and then buy a new, or newer, airplane. As shown by the chart, the price of a new 172 was historically less than twice the U.S. median wage. Now it’s more than seven times. So you either keep overhauling your ride, sell it and get something else used, or get out of the game.

Airplanes have become a boutique market, and General Aviation cannot survive in a boutique market.

24

And an engine failure on a twin gives the pilot options, while in a single there is only one option. So you have twice the chance for a failure and if you do have a failure you have some decisions to make. In general the outcome of those decisions needs to be twice as good as the outcome of a single having a failure to make up for the increased chance of the failure happening. This is a big ask and relies on twins having adequate performance at max weight (many don’t and they’re not required to) and pilots having the skills to both fly safely on one engine and make appropriate decisions.

My take-off self brief in light twins (Islander and Aerocommander) was to clean it up, assess performance, and decide. If it’s performing then we continue if not then we land straight ahead. I never had to find out how good my skills and decision making really was because I never had a problem that required them, though I did abort a take-off after a magneto shat itself.

I don’t think a light twin flying privately should necessarily be able to climb away on one engine, but the pilot needs to know what it can and can’t do and how to achieve it.

25

There is very little that can be done design wise. Yes you can add more engines, but these tend to be rejected by the universe as being too ugly and haven’t been a big commercial success (large passenger jets aside).

There are other minor changes that can be made such as having contra-rotating props so that the thrust line* is inboard of both engines instead of inboard of one and outboard of the other leading to the concept of a “critical engine.”

The process of securing the engine can also be made easier. In light twins the pilot must physically confirm which engine has failed and then feather the prop themselves. If they don’t feather the prop they will crash and if the identify the wrong engine they will also crash. An auto feather system will automatically feather the prop when a failure is detected leaving the pilot to just fly. The downside of an auto feather system is that false positives can create more problems than they solve.

There are some sectors of the industry that are moving to singles instead of twins. The problem with singles, even turboprops, is that it is very hard to get regulatory approval to fly fare paying passengers in instrument conditions in a single engined airplane.

Some branches of the Royal Flying Doctor Service in Australia have made the switch from Beech Kingairs, a twin turbo-prop, to Pilatus PC-12s, a single turbo-prop. But these are air work operations, not air transport, and they do a lot of training to deal with a failure in cloud, at night.

This is all largely irrelevant to the discussion on private airplanes though as few private individuals can afford a current era turbo-prop and there is no great hurry to design any aimed at the private sector. It seems that manufacturers think if you can afford a turbine engined airplane, you may as well be getting a jet, hence the marketing of VLJs such as the Honda Jet.

  • The thrust line from a propeller is not aligned with the centre of the prop but is offset toward the side that is rotating downward. Due to the fact the airplane itself flies at a small angle to the relative airflow in order to create lift over the wings, the down going blades have a slightly higher angle to the airflow and create slightly more thrust. Many light twins have identical engines on each wing which means that the thrust line on one wing is outboard of the engine resulting in more asymmetry in thrust when the other one fails.
26

Good points all. I wasn’t real specific about how I thought the FAA & manufacturers contributed to the problem, and you misread my mind. :slight_smile: Here’s what I meant.

I agree that the FAA did *not *kill GA through ever-increasing regulation strangling it as you tried to debunk.

Instead they stopped updating the certification regs to account for progress. They in effect enforced a requirement to build a 1950s-tech airplane in 2005. Which was death since 2005 customers did not want to buy a 1950s product.

The FAA, despite their good intentions towards safety, all but killed innovation in GA. Which is how we get homebuilts with glass cockpits and modern engines and high performance. But none of whose components can be legally installed in a C-150.

FAA has since woken up and is starting moving the other way, mandating not how to build a structure or a fuel pump but rather what its reliability must be. Ironically composite structures in airliners and control systems in drones are the poster children for FAA abandoning “how” for “results”.
The manufacturers ended up bailing out during the great 1980s hiatus as each traditional airplane factory run by airplane people was sold to one or another conglomerate which then ignored / starved of capital their airplane division into insignificance. Having left the public with no choice but to maintain & upgrade used but durable airplanes, they killed the demand for their products for good. They certainly killed demand for newly built obsolete designs with stylish new paint jobs. Which was all the last of Cessna’s and Piper’s products were.

During the hiatus was when outfits like Cirrus and LancAir got their starts; building a modern factory type airplane while they carefully tiptoed up to the edge of the regs on percentage of owner construction effort.
You’ve hit the nail perfectly on the public’s response to all this and the deadly price vs. volume spiral that has engendered. As you say, private hobbyist GA cannot survive as a boutique market.

Or at least that’s how I see it.

27

I think this is inaccurate. ISTR that when production restarted, the new aircraft were certified under newer, more stringent (for safety) rules. The 172S Skyhawk and the 182T Skylane are built under the new rules, but Textron decided it would be too expensive to bring back the 210 under them. (I’m going on memory here, and I can’t find a cite.) But yeah, the 172s and 182s and PA-28s are '50s/early-'60s technology, except insofar as they were updated for the new rules. Which is why people objected when the re-introduced Skyhawk was listed at $175,000. (Current base price, $369,000.) Why spend more than a third of a million dollars for what was designed as, and marketed as, an entry-level airplane for middle-class owners?

Nevertheless, there’s nothing wrong with the decades-old basic design. If they were middle-class affordable, as they used to be, I’d certainly buy a new Skyhawk. With a modern panel, it’s a modern plane. Well, except for the 1930s technology engine. :frowning:

In my cynical view, they don’t want to build piston-singles. It’s more profitable to build jets. IMO, they’re looking at short term profits and completely neglecting that soon there won’t be anyone to fly their money-makers.

And there’s the rub. When you’re in a positive feedback loop, you need to take drastic action. People won’t buy airplanes unless they can afford them. And airplane makers need to generate positive publicity to get the public interested/re-interested. Only when they can realise economies of scale will airplanes become affordable (for a given value of ‘affordable’). They need to come out with a ‘loss leader’. But that’s long-term thinking, and I don’t think they’re into that.

And then there’s the whole political policies that have diverted wealth from the middle-class – the actual Market – into the pockets of the wealthy. Consumers don’t consume when they have no money.

28

I almost asked about that earlier in the thread. I remember a conversation some years ago with my uncle when he said he’d never own a twin-engine airplane, and he mentioned that as one of the reasons; too unforgiving when one engine fails, especially the critical one.

That’s why I wonder if they might be able to bring some clever engineering to the problem. If just the thrust line of the downward spinning prop makes such a difference, it seems like there might be some more ideas worth trying. If a push-pull configuration (like the Skymaster) doesn’t work, how 'bout twin pushers on the back of the fuselage, as close together as possible, and twin booms to support the tail? Or keep the push-pull layout but mount the rear engine higher like on a Lake or a Republic Seabee?

As it happens, my last flight in a small plane was a few years ago in Montana. My uncle took me up in his Bonanza. He told me the model year but I don’t remember, 2003, 2004, something like that. Had mechanical flight gauges and a Garmin unit for the radios. Paint job was very stylish.

My uncle seems partial to Bonanzae. I remember he had a v-tail one back in the '70s.

29

This quote seems pertinent to the discussion.

30

Cite? I mean, you’ll not find a greater Skyhawk fan than I am. But what about airplanes with lower landing/stall speeds?

31

I don’t remember where I heard it, maybe the AOPA board or perhaps the EAA one. I should have included one of these, :slight_smile: , because I’m sure it was meant as a wisecrack.

The “aluminum parachute” line still gets a chuckle in the shunpiker house.

32

Well… maybe…

But aside from the landing characteristics, a C150 or C172 has very robust landing gear that will either provide some shock absorption from a hard landing, or will NOT be ripped off by the roll-out through a rough field (I speak from experience on the latter). You also have at least some structure around you/your passengers

While some of the kitplanes and ultralights I have flown have had lower landing and stall speeds quite a few of them offer little or no protection for the occupants.

I don’t want to crash an airplane but yeah, I can argue that a C172 would be one of the safer options assuming the pilot has some control over the situation.

The Stearman biplane might be another option - it’s sort of overbuilt, the frame is steel, the upper wing sort of provides some protection in an overturn situation, and it’s the only airplane I’ve ever know to win an argument with a full grown pine tree - but they aren’t exactly common anymore.

33

A Stearman sits on pretty tall narrow gear. If you land in soft terrain and nose it over onto its back the front seat occupant is probably OK if his/her belts are tight. The tail usually crushes or digs in enough to smash the back seat pilot’s head into the ground. Not good. Damn near happened to my Dad. :eek:

34

Hmm… good point.

They are kinda squirrely with ground handling, which just complicates emergency landings.

Of course, I’m pretty short, I might be able to duck down past the steel frame of the fuselage, but I’d rather not bet my life on it.

Yep, let’s go with the C172 for crashworthiness.

35

Also a straight tailed early C-150

36

I know of one incident where a student in a 150 hit an arresting cable with the mains at a National Guard base. Best short field landing ever.

37

Won’t someone think of the zero-engine aircraft? You never need to think about an engine quitting. (To be sure, you always have to think about not having one to begin with.)

38

True. And such a zero-engined aircraft will sometimes perform better than a twin with one failed!

39

Given that zero engine aircraft just sit there motionless until an engine somehow delivers them to altitude, I think they’re especially safe. Zero knots is IMO the ideal speed to collide with the ground.

40

Unless you stall one after you have been towed to 20k and make yourself a big silent lawn dart.

A thing is only as safe as the guy in the seat.