Rabenschlag From Germany, joined Oct 2000, 968 posts, RR: 1 Posted (9 years 10 months 21 hours ago) and read 4370 times:
with improved reliability of jet engines, is it conceivable that one day there will be a single engine jet? like a 777 with only one powerful turbine located in the rear of the fuselage?
Pmk From United States of America, joined May 1999, 664 posts, RR: 2 Reply 2, posted (9 years 10 months 21 hours ago) and read 4312 times:
Well the FAA is not going to allow it for a while. I will say that there is a business jet called the Visionaire Vantage that is still undergoing certification that is a six seat exec jet with only one P&W engine. Supposed to be certified for part 135 OPS.
Md88Captain From United States of America, joined Nov 2001, 1258 posts, RR: 24 Reply 3, posted (9 years 10 months 20 hours ago) and read 4260 times:
Single engine jet? With passengers? Not for this pilot. Yes, they are reliable, but not 100% reliable. They quit every so often, like 2 days ago on the DAL 757 coming out of SNA. Ask those guys if they want to fly a single engine passenger jet. Flying single engine/single pilot while strapped to a Martin Baker ejection seat is acceptable risk for many thrill seekers. But a single engine passenger jet is just asking for death and destruction.
Backfire From Germany, joined Oct 2006, 0 posts, RR: 1 Reply 5, posted (9 years 10 months 19 hours ago) and read 4198 times:
Civil aviation safety is based on a fundamental premise: redundancy of critical systems, regardless of reliability.
Single-engined commercial flights? IMHO it'll be allowed the day after the engine is designated a non-safety-critical part of the aircraft. Work out for yourselves how long that'll take...
Rabenschlag From Germany, joined Oct 2000, 968 posts, RR: 1 Reply 8, posted (9 years 10 months 18 hours ago) and read 4164 times:
now that so many of you find it to be unlike, just think about the following two thoughts:
a) it's not about redundancy per se, it's about probability of a complete loss. i think it is at leas conceivable that one will be able to build an engine that is less *likely* to fail than two engines at a time (e.g. two first generation jet engines).
b) there are many one engined prop's and nobody cares. there are even large ones that may carry 6 pax or more (like the pilatus).
sooooo, perhaps its not an obvious development but not impossible, or is it?
N79969 From , joined Dec 1969, posts, RR: Reply 9, posted (9 years 10 months 18 hours ago) and read 4151 times:
I think 6 seats is still general aviation and not transport category. The engines used on the 767,777, and the 330 have reached a point of near 'fail-safe' meaning that they cannot really become a lot more reliable than they are already. In spite of that, no aviation authority will certify a single engine transport airplane. Governments can't take the political risk of certifying a single engine transport that may crash due to engine failure. Passengers won't like it psychologically.
Backfire From Germany, joined Oct 2006, 0 posts, RR: 1 Reply 10, posted (9 years 10 months 18 hours ago) and read 4132 times:
Rabenschlag,
Redundancy has everything to do with it.
It doesn't matter if you build the most reliable engine in history. What matters is that you have a backup for the day it goes wrong.
I haven't done the maths but the probability of a single-engine failure today might even be lower than that of a dual-engine failure on a older twin-jet (DC-9, 737-200, etc). Yet we've never used that reliability to justify eliminating redundancy.
Mcdougald From , joined Dec 1969, posts, RR: Reply 11, posted (9 years 10 months 18 hours ago) and read 4124 times:
One of the main obstacles to a single-engined jetliner would be passenger confidence. No matter how reliable the engine is, many people would have a bad feeling in their gut about it. The reliability statistics wouldn't mean a thing to them.
For instance, if someone does business with a store or restaurant 20 times and gets treated shabbily only on the 20th visit, there's a good chance they won't go back for years. The statistical fact that they were a satisfied customer 95% of the time and a dissatisfied one only 5% of the time won't matter, or that the probability of it happening again might be fairly low. All they'll think about is that the place gives them a bad feeling in their gut.
Now imagine if one of these planes crashes due to engine problems. Even if it was an isolated accident and the engine boasts a 99.99999% reliability factor, the media will repeat over and over again that it was a one-engined plane with no backup in case that one and only engine failed. That would be enough to give millions of viewers that same bad gut feeling.
Rabenschlag From Germany, joined Oct 2000, 968 posts, RR: 1 Reply 12, posted (9 years 10 months 18 hours ago) and read 4101 times:
Mcdougald,
i like your analysis. humans have big psychological troubles dealing with risks or dealing with very large and very small numbers in general. still, airbus luckily failed to persuade people that twins are something one should be afraid of. so they have a hard time to sell the four(money)holers. what if airlines could drastically cut costs with oneholers?
backfire,
i'm not completely convinced yet. in a way, redundancy is a way to reduce a certain risk. cutting risk is the end, an redundancy is ONE means to do so. we had no problem to sacrifice the redundancy of four engines to two engines as two have the same risk as four. or isnt it?
SailorOrion From Germany, joined Feb 2001, 2058 posts, RR: 7 Reply 14, posted (9 years 10 months 16 hours ago) and read 4041 times:
A critical system must not have a failure rate of more than 10e-9 / flight or flight hour. Jet engines are still lightyears away from this threshold, so there will be no single engine aircraft certified after Part 25 FARs / JARs in the foreseeable future.
Cointyro From United States of America, joined Aug 2001, 62 posts, RR: 0 Reply 16, posted (9 years 10 months 16 hours ago) and read 4025 times:
Don't forget, there are loads of people flocking to Sir Richard's four-holers crossing the Atlantic instead of the passe 763 merely on the proven pyschological tendency for passengers to avoid any ETOPS situation, no matter how inconceivably unlikely. Crazy but true - and paying-passenger demand is what dictates what we fly just as largely as efficient operations.
People play the lotto don't they? Obviously people don't have a grasp on numbers outside the 0.01% to 100,000% range. Hence Branson's A340s and 744s jumping the pond on the shorter side of their endurance curves.
Srbmod From United States of America, joined Mar 2001, 16224 posts, RR: 57 Reply 17, posted (9 years 10 months 13 hours ago) and read 3945 times:
AIRLINERS.NET CREW HEAD MODERATOR
Airliners have had two engines minimum since the 1920s, when regs were put into place requiring airlines to fly a/c with at least two engines. This was in response to the TWA crash in which Notre Dame football coach Knute Rockne was killed. That aircraft was a single engine airliner, and after that crash, that type of a/c left commercial service (unless you count some of those Air Taxi services in AK that use Cessnas). When the jet age arose, the engines were not powerful enough to only use two engines, and add to this reliability issues with the early engines, and 4 engines made sense. Up until Airbus built the A300, the largest aircraft with two engines were the DC-9, the BAC 1-11, the Caravelle, and the 737. As technology has gotten better, newer designs allowed two engines because of the newer engine technologies made it safe and practical. Some aircraft have to have 3 or 4 engines just to get it off of the ground.
Hello Airplanes? Yeah, it's Blimps. You win, bye....
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 44 Reply 18, posted (9 years 10 months 13 hours ago) and read 3944 times:
Don't forget, there are loads of people flocking to Sir Richard's four-holers crossing the Atlantic instead of the passe 763 merely on the proven pyschological tendency for passengers to avoid any ETOPS situation, no matter how inconceivably unlikely. Crazy but true - and paying-passenger demand is what dictates what we fly just as largely as efficient operations.
Well, you may be correct but I don't think so. The vast majority of pax don't know what type of aircraft they're sitting aboard, never mind how many engines are under the wing. They may be flocking to Virgin Atlantic but most likely for other reasons.
Delta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 9 Reply 22, posted (9 years 10 months 8 hours ago) and read 3814 times:
High reliability only means that there is a very low failure rate, but there is still a failure rate, nonetheless. That means that an engine will fail, only we don't know ahead of time when that will be.
There are two aspects to risk management -- one is to reduce the likelihood of occurrence of a bad event, and the second is to limit the severity of the event when (not if!) it occurs.
We accomplish the first by making things as reliable as possible. We accomplish the second by adding redundancies. Any chain of events that will lead to catastrophic event (a fire, loss of control, etc.) must not be greater than 1e-9, as someone noted above. So, we have to keep adding redundancies until all identifyable chains of events can be shown, at least on paper, to meet this safety requirement. This is why a passenger plane must have at least 2 engines.
All airframers have a department staffed by mathematicians and engineers called Reliability & Safety Engineering -- it's one of the most important disciplines in aircraft design. Their analysis ultimately dictates the architecture of the electrical, hydraulic, flight control, fuel and avionic systems, just to name a few. The high level of safety in aviation does not happen solely by keeping the planes maintained, but even moreso by the inherent design. As they say, "Safety is no accident."
Gr8slvrflt From United States of America, joined Jan 2002, 1566 posts, RR: 18 Reply 23, posted (9 years 10 months 7 hours ago) and read 3805 times:
Airliners have had two engines minimum since the 1920s, when regs were put into place requiring airlines to fly a/c with at least two engines. This was in response to the TWA crash in which Notre Dame football coach Knute Rockne was killed. That aircraft was a single engine airliner, and after that crash, that type of a/c left commercial service (unless you count some of those Air Taxi services in AK that use Cessnas).
Knute Rockne was killed in the crash of a TWA Fokker F.VII trimotor. The cause of the crash was structural failure of the wooden wing due to internal rot. This crash spelled the end of wooden airliners in the US, not single-engine airliners. Lockheed and Northrop single engine planes were used for passengers until banned by the Civil Aeronautics Act of 1938. Before then, single engine aircraft offered superior speed than contemporary multi-engine types.
Brianhames From United States of America, joined Feb 2000, 795 posts, RR: 3 Reply 24, posted (9 years 10 months 7 hours ago) and read 3799 times:
Yeah, you'd need ESOPs
25 Cloudy: A few points - 1. It is my understanding that for airline operations a jet must be able to suffer an engine failure on takeoff and continue to climb,
26 Gr8slvrflt: What about a second engine for takeoff that would then be shut down and retracted or faired-over for cruise? This engine could also be brought into se
27 Jetguy: Cloudy made an interesting comment... In general aviation, twins have a higher accident rate than equivalent singles. Twin engine airliners have a low
28 FDXmech: Excellant post Delta-flyer. The reasoning of four engines being good, three being better and two better yet so why not one defys logic and is readily
29 L-188: The problem isn't with the engines it is with the flight controls to the tail. The problem is that the most logical place to put a turbine engine woul
30 Rw774477: ..... and in the unlikely event of an engine failure, we all die ... thank you for flying Air ..... rw774477
31 Eugdog: Aviation safety is determined by cost per life saved (currently $3 million per life)- this means that the cost of any saftey measure divided by lives
32 FredT: When flying a single engine aircraft, you are to fly it in such a way that if an engine fails at any time in flight, you can handle it. That means alw
33 Delta-flyer: Redundancy increases safety but so does simplicity. There is a trade-off. Excellent observation, Cloudy. This is what we, engineers, contend with all
34 Klaus: Cloudy: Twin engine airliners have a lower diversion rate than quads do. You´re making a popular mistake, here. A quad has a slightly higher chance o
35 Airplay: FAR 25 901(c) states: (c) For each powerplant and auxiliary power unit installation, it must be established that no single failure or malfunction or p
36 Skyguy11: "Single engine jet? With passengers? Not for this pilot. Yes, they are reliable, but not 100% reliable. They quit every so often, like 2 days ago on t
37 PPGMD: Not really going to get in this debate, but the Air Canada's 767 Glider, was calculated to have a 14:1 glide ratio. Thats about the same as a Cessna.
38 FDXmech: The point you´ve missed, however, is that a quad will still remain in a multiple-redundancy mode, while the twin is in a clear and direct emergency w
39 Klaus: FDXmech: Can you point to a twin that suffered a dual engine failure other than failure caused by environmental factors (volcanic ash, flock of birds,
40 T prop: Single engine pax jetliner? Not in our life time, see all of the reasons above. Twins vs quads IMHO: Trying to select flights on quads because one is
41 Klaus: T prop: You have a much higher chance of being struck by lightning, bitten by a shark or killed on the way to the airport. Might I remind you that mos
42 FDXmech: Klaus There seem to be quite a few cases of "overshoot" where people apparently seem to believe twins were somehow safer than quads. Of course entirel
43 PPGMD: There is already an aircraft that can serve the A340's market. The funny thing is that it has been available for years. The problem with Airbus is tha
44 Klaus: FDXmech: I do find it ironic that, Airbus, who pioneered the widebody twin is now putting its money on several quads. Which seems quite consistent, si
45 T prop: Might I remind you that most people do seem to be using lightning-conductors, get out of the water when a shark is in sight and try to drive cautiousl
46 FDXmech: Klaus Basically betting the farm on none of their twins ever having a double inflight shutdown. The first such incident would probably yank the priori
47 Cloudy: Klaus - I was not talking about ETOPS, I was talking about the possibility of engine failure at altitude. I never claimed you could glide to a safe la
48 Rabenschlag: puh, this has turned into a 2 vs. 4 discussion. just let me try to summarise and add a new thought: a) most of us reject single engine AC because we t
49 Md11nut: In some of the posts, only part 23 and 25 were mentioned regarding multi-engine requirements. I'd like to point out that the answer lies elsewhere. Pa
50 PPGMD: Ummm MD11nut forgive if I am wrong, but I do remember that there are a few Caravans operating 121 routes.
51 Klaus: FDXmech: So in your mind, ETOPS, no matter how many decades of proven, safe and reliable service can never be fully accepted on the premise of an even
52 Klaus: Cloudy: Engine failure, alone and at altitude, hasn't been a problem in commercial jets - at least not for some time. When the 777 was designed - engi
53 Pmk: Folks: I fly in a single engine turbo prop capable of carrying nine passengers, two crews and is FAR135 Certified. I have absolutely no quams flying i
54 Airplay: MD11NUT, Part 25 does in fact prohibit the design of single engine aircraft in the transport category albeit indirectly. How else can you meet the req
55 FDXmech: Klaus No, that´s not my point. I just object to the apparently spreading illusion that the added redundancy of a quad was meaningless. Risks can (and
56 Klaus: FDXmech: I would like to know in your opinion how FBW has increased potential for safety versus mechanical control in the same respect of raw redundan
57 Julien.M: have a look at that! http://technology.grc.nasa.gov/success/industry/century.pdf
58 MD11Nut: Airplay:"Don't mix design standards with operational standards. It can make this discussion very confusing." Airplay, with due respects, by using part
59 B747skipper: Why not a single engine jet - right my friends... There are plenty for sale right now, from old T-33s to MiG-27s... Whether I am a "passenger" and car
60 Airplay: MD11Nut, That big old parachute will just slow the descent into the dark ocean.... I disagree that there is any way to satisfy FAR 25 with a single en
61 Cloudy: Klaus, Thank you for your reply and your points. We may be closer together in thought than I had believed -From what I heard, the A340 actually runs i
62 Lapa_saab340: I don't see how a single engine passenger jet would ever be manufactured, nor how anyone in his right mind would want to fly on one. It doesn't matter
63 L-188: Why are we so afraid of single engine jets. We have flown behind single engine pistons, and turboprops for years.
64 Lapa_saab340: Heya L-188 That was the point I was trying to make. Flying a single engine piston or turboprop is a different story from flying a large single engine
66 L-188: One other thought that was just brought up by a pilot reading my last posting over my shoulder..... When you are flying at 40,000 feet you have a lot
67 Jetguy: Just a couple more things to throw into the fray... By regulation, certified civilian single-engine aircraft - regardless of the type of powerplant -
68 FDXmech: Klaus I guess to put it in a nutshell, I feel you display a sorta double standard in regards to redundancy (not meant as hard is it might read ). You
69 Lapa_saab340: Hey again L-188 I think we're talking about two different things. From what I understood from the first post, Rabenschlag was wondering whether a sing
70 Klaus: FDXmech: I guess to put it in a nutshell, I feel you display a sorta double standard in regards to redundancy Well, of course; You just can´t have en
71 FDXmech: Klaus It´s not just some traditional superstition; Redundancy is fundamental to safety with every technology - even nature has always applied it with
72 Klaus: FDXmech: Of course redundancy is fundamental with safety, the quandry is you're personnally and might I say subjectively picking and choosing what you
73 T prop: FDXmech: As far as first generation Airbus FBW being as redundant or fail-safe as traditional systems, do you recall the Lufthansa A320 with reversed
74 Klaus: T prop: I don't agree, IMO the FBW system got them into the mess in the first place. On a transport category jet with conventional controls it is IMPO
75 T prop: If you crossed the two opposing cables, you??d probably end up the same way. If it??s difficult to overlook - good! With FBW, that can be achieved as
76 ThirtyEcho: Lets face the economic issue as well; this applies to a C310 and everything else that flies with engines. The fact is that single engine A/C have no c
77 FDXmech: The evolution of your thoughts on FBW. Klaus: That´s what I said before, basically. The point is that this makes it easier to meet increased demands
78 Klaus: T prop: Have you ever replaced or rigged control cables? If you did you'd know that on a transport jet they CANNOT be misconnected, it's not physicall
79 FDXmech: Klaus: Wires age much more slowly than moving parts. In addition, connected systems can monitor decaying signal quality and interference events to hel
80 Klaus: FDXmech: Guess you haven't seen aircraft wiring thats been in service for a while, especially that's exposed to the harsh environment. If you have, yo
81 Pmk: Cloudy: I don't mean to throw gasoline on an already raging inferno, but you need to be reminded or perhaps informed of a scarry/dangerous fact about
82 Klaus: Pmk: There is no inherent safety in FBW, in fact the opposite. Of course FBW isn´t some kind of magic Voodoo which makes planes safer by its mere pre
83 Airplay: Pmk, We all know that pilots are responsible for the vast majority (about 80%) of aircraft accidents. I'm not passing judgement just regurgitating sta
84 FDXmech: Klaus: There are certainly reasons to be extra careful with the introduction of FBW systems. But your bias seems a bit over the top, at times. How muc
85 Airplay: This would be a good time to discuss the non-FBW disaster involving a DC-10 and a corn field in Iowa. An uncontained engine failure knocked out ALL of
86 FDXmech: I also have to disagree that cables are hardier than wires. Cables suffer wear with use. Wires tend to suffer from weather. The effects however usuall
87 Airplay: We're getting off topic....but it's a natural evolution of the original question... Non-existent? Extremely rare? The FAA disagrees with you. Just che
88 FDXmech: Airplay: There are MANY more. If you include small aircraft it gets unbelievable. Obviously in the grand scheme of things, this sort of thing is not w
89 Klaus: FDXmech: You're right, I'm getting a little carried away trying to prove my point. Because of this I'm coming off as anti-FBW/high tech, I am not. My
90 Klaus: FDXmech: I've been working large commercial jets on the line and out of service crews for 20 years and personnally saw less then a handful of cable fa
91 Airplay: I stand by my earlier statement: ETOPS is a money-saving scheme that accepts second-grade safety (relative to well-engineered and -maintained quads) o
92 FDXmech: Klaus: With FBW (or "fly by light" in the foreseeable future), there is no real tradeoff to be made. Systems will have to be designed and maintained p
93 FDXmech: Klaus: With ETOPS, however, it´s a good idea to imagine the next step - as Rabenschlag did with this thread - and think of "ESOPS": "Extended Single
94 FDXmech: Klaus: I stand by my earlier statement: ETOPS is a money-saving scheme that accepts second-grade safety (relative to well-engineered and -maintained q
95 Klaus: Klaus: With ETOPS, however, it´s a good idea to imagine the next step - as Rabenschlag did with this thread - and think of "ESOPS": "Extended Single
96 FDXmech: Klaus, your exasperating. Klaus: When it´s about the validity of the ETOPS concept (removing redundant engines while improving other systems), this i
97 AA_Cam: Although I do agree with the general consensus formed at the begining of this forum, I would rather be in control of a Piper Warrior, when it looses i
98 Klaus: FDXmech: Klaus, your exasperating. Thank you. I can only return the compliment. FDXmech: It's beyond me how you can draw any kind of objective, logica
99 Airplay: I had to laugh at this excerpt from Klaus's post: FDXmech: I can't argue nor would I the moot point of single engine Part 121 ops, it is a fantasy or
100 Airplay: Some additional thoughts..... Adding engines does not always increase safety. It does however allow longer exposure to the possibility of a fault duri
101 Notar520AC: If single engine jets aren't popular, or reliable, as some of you think, why are the F-16 sales peaking? Why is NASA looking to develop single engine
102 FDXmech: FDXmech: Well this is part of the problem. Redundancy or not depending on the designer considering all possible scenarios. Klaus: I beg your pardon? I
103 Airplay: Notar, Nobody is debating the usefulness of single engine aircraft in military, personal or experimental roles. We are addressing safety in commercial
104 Loadcontroller: After reaching take off speed, HB-IWM (MD11, LX292 to NBO and DAR) on last Wednesday had a bird strike in the engine located at the top of the aft fus
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