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Hauldren Collider posted:See, I just flat out don't believe this. My car puts out a pretty constant 2000+ RPM on the highway at speed, same as a Cessna when cruising, has absolutely no problem powering up steep hills while going 75+ mph, and I SERIOUSLY doubt Honda would have much difficulty modifying a car engine for whatever minor difference in performance is required for an airplane anyway, particularly given past success and the capabilities of modern automobile engines. The issue is that a typical small car only requires somewhere around 35HP to maintain highway speeds, which means it's turning at 2500RPM, but it's only putting out around 25% (assuming a 150hp engine) of it's rated power to do so, and is turning nowhere near it's maximum RPM. From calculations I could find online, even climbing a 5% grade at 70 mph, the engine only needs to produce about 50% of rated power, which should still be well under the redline RPM. On a Cessna 172 with only slightly more power (160HP), the engine is expected to run at full power during takeoff and climb (maybe 10-15 minutes, and with reduced cooling airflow), and in cruise, it'll be running at 65-75% power, while turning at somewhere around 80-90% of redline. Properly maintained and operated, most small airplane engines can comfortably do this for somewhere beyond 2000 hours before they'll need an overhaul. I'm guessing that running the engine in a typical Honda or Toyota on that same cycle would result in some kind of catastrophic failure well before it hit the 2000 hour mark, largely because having the internal bits of an engine only moving at 23-2500 RPM for sustained periods is a lot less stressful on things like pistons, valves, and connecting rods than spinning at 5-6000 RPM would be. azflyboy fucked around with this message at 04:00 on Aug 3, 2015 |
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Aug 3, 2015 03:57
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Yeah I don't think an aircraft engine producing constant power to a crankshaft to a prop without any gearing is analogous to modern car engine setups at all.
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Aug 3, 2015 04:04
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Most auto conversions derate the peak horsepower considerably. In fact most aircraft engines redline way below the horsepower peak because they wouldn't last if they ran at peak power. This reminds me of a conversation I had with an avionics tech at Oshkosh. I work in the power industry on electronics so it was nice to speak to someone who was not a salesman. They were selling ADS-B out equipment and he explained to me how the WAAS GPS source was around $1500. He really didn't have a good response to what it did differently than one of these. http://www.amazon.com/GlobalSat-WaterProof-WAAS-Enabled-Receiver/dp/B006PH0GBA They are using certification costs as an excuse to massively inflate the price of items like this. Buy an off the shelf WAAS GPS chipset that is rated for high and low temperatures, install it in an alodined aluminum box and put in some nice filter caps and a mil-spec dsub connector. You just increased the value of that chipset by an order of magnitude.
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Aug 3, 2015 04:09
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You're paying someone to take legal responsibility for it to work in a life or death situation.
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Aug 3, 2015 04:12
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Hauldren Collider posted:See, I just flat out don't believe this. My car puts out a pretty constant 2000+ RPM on the highway at speed, same as a Cessna when cruising, has absolutely no problem powering up steep hills while going 75+ mph, and I SERIOUSLY doubt Honda would have much difficulty modifying a car engine for whatever minor difference in performance is required for an airplane anyway, particularly given past success and the capabilities of modern automobile engines. The Honda is making perhaps 10% of its rated power at 2k RPM on the highway. Power setting =/= RPM. Try driving it with your foot almost completely matted to the floor for two hours at a stretch, and let me know what fails first; And it WILL fail. An O-320, on the other hand, you can push the throttle all the way in, and loving LEAVE IT THERE until it runs out of fuel, and it'll be perfectly happy, as long as you have the mixture set halfway properly, and are going fast enough to keep it cool. However, even at 100% power, it's probably only turning 2700rpm. Car engines, as explained above, are designed to produce high peak power, but aren't generally expected to produce even 50% power for more than a few dozen seconds, or perhaps a minute or two at a time. The majority of the time, they are just ticking over, running accessories, and providing the minimal amount of power required to push the car down the road (Its something like 15-25hp at 65mph.) This leads to manufacturers building engines that will not survive extended periods at high power/RPM, and if subjected to such, you start to see fun things happen. Another fun fact: something like 80% of the engines installed in GA aircraft DON'T require 100LL, and in fact, quite a few of them were certified on 80/87, and would very happily run on mogas (in fact, the aforementioned O-320, as well as O-200s, O-470s, and O-300s will actually run better on 87 or 91 octane mogas than they do on 100LL,) if you could still get it without
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Aug 3, 2015 04:15
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Another issue is that even if an automaker were to decide "Let's make piston airplane engines!", the investment needed to convert a car engine to work reliably in an airplane would probably never pay itself off, even ignoring the cost of FAA certification. As an example, GM sells about 34,000 Corvettes each year (which is small potatoes by car standards), whereas worldwide, there are maybe 1000 piston engine airplanes sold every year, so the economies of scale simply aren't there for something operating on the level of a carmaker.
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Aug 3, 2015 04:28
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azflyboy posted:Another issue is that even if an automaker were to decide "Let's make piston airplane engines!", the investment needed to convert a car engine to work reliably in an airplane would probably never pay itself off, even ignoring the cost of FAA certification. *coughcough*Thielert.
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Aug 3, 2015 04:46
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MrChips posted:*coughcough*Thielert. ...And we see how well THAT'S gone off, haven't we?
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Aug 3, 2015 04:57
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MrYenko posted:...And we see how well THAT'S gone off, haven't we? Not only that, but the Ghost of Thielert Past continues to haunt Diamond in the form of Austro Engine.
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Aug 3, 2015 06:03
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Probably a better comparison would be a marine diesel or gasoline outboard motor, which also runs at 100% of rated power all day long. Those are not significantly expensive, they're mostly just tractor engines with a two stage water coolant system and higher quality lubricants and gaskets. We ran my buddy's marine diesel in his sailboat for two days straight coming back from Corpus Christi to Houston last year (try refueling a boat while underway in 6 foot choppy seas using a Jerry can) That said, the limits of a car's engine is generally it's cooling system, which yeah, are generally undersized given their workloads. There's no reason to think that if you upgraded to a 4" thick radiator from the stock 1" radiator, that the engine couldn't run at peak power for longer periods of time, if not indefinitely, although it's possible some hot spots could form given a long enough time period. Those aviation engines were probably all designed and built before the convenience of modern computer design hardware where you can accurately model expansion of materials during heating and cooling, and relative difficulty of getting quality parts. The light aviation engine industry is probably long overdue for a big shake up.
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Aug 3, 2015 07:26
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Hadlock posted:Probably a better comparison would be a marine diesel or gasoline outboard motor, which also runs at 100% of rated power all day long. Those are not significantly expensive, they're mostly just tractor engines with a two stage water coolant system and higher quality lubricants and gaskets. We ran my buddy's marine diesel in his sailboat for two days straight coming back from Corpus Christi to Houston last year (try refueling a boat while underway in 6 foot choppy seas using a Jerry can) Marine engines are also unsuitable for aircraft. I can't think of an engine type more unreliable than an outboard motor and while I will concede that their operators beat the living poo poo out of them most of the time, you'll find that your average outboard motor is really only good for a few hundred hours of operation at most before they're completely trashed. As for marine diesels, they tend to have very low power density (power per unit of mass) - lower than any on-road application and certainly lower than any aircraft engine; a good part of this reason is, apart from the fact that most diesel engines use extremely heavy cast iron engine blocks, the issue of the cooling system. As we all know, weight and drag are absolutely critical in aircraft design, and a totally liquid-cooled engine suffers in both of those areas compared to a straight air-cooled engine. The radiator, hoses, valves, tanks and even the coolant itself adds weight and takes away precious payload, to say nothing of the additional drag needed to fit a properly-sized radiator. For all that piston aircraft engines get poo poo on constantly, their power density is almost unrivaled among reciprocating engines that aren't designed for racing purposes. As for converted automobile engines, the problems run much deeper than just the cooling system. High-load operation puts incredible strain on the entire engine but specifically on valve springs, camshafts, connecting rod bearings, wrist pins, piston skirts and rings. All of these parts would need to be specially made for the conversion engine, as they don't really exist in the automotive world. The issue of cooling comes up again; not for the liquid cooling circuit but for the oil and the parts it is responsible for cooling, such as the entire array of reciprocating and rotating parts in an engine. This means you would need to increase engine oil capacity (heavy and possibly very draggy) add all kinds of specialised and/or heavy duty parts like piston squirters, high-volume oil pumps, probably some sort of scavenge system from the cylinder head(s) and likely a very large oil cooler, as this engine would put enormous thermal stress on the engine oil. Vibration is another serious issue, especially with diesel engines. Almost every automotive engine relies on a flywheel to dampen out the pulsating forces generated by the individual combustion events each rotation as well as keeping the engine turning between these events. While a propeller is an effective solution for the latter, it actually causes more problems than solutions for the former issue; more often than not, the propeller accentuates these vibrations, which is very hard on the engine, the engine mounting structure and the operator alike. But the single largest obstacle for automotive conversions, where just about everybody has gone wrong, is the reduction gearbox. Automobile engines typically produce maximum horsepower at 5500-7000 RPM, which is far too high for any propeller to be driven directly off the crankshaft. Therefore a (heavy, complicated, failure-prone, thermally-sensitive) reduction gearbox is needed to turn the propeller at it's optimum RPM, which for most general aviation aircraft is in the 2500 RPM range. Additionally, certification requirements these days require some sort of disconnect mechanism between the propeller and the gearbox to minimise damage in the event the propeller suddenly decides it's done turning for the day (usually with the help of the ground). All of these issues, combined with the vibration issue I mentioned before, have proven to be nothing short of a daunting challenge for any prospective engine builder. As yet, nobody's really figured out a way to create a gearbox large enough to absorb the 300-350 bhp of the engine, the vibrations associated and have it be just as cheap reliable, cheap and lightweight as a direct-drive engine - this is where both Thielert and Austro have fallen flat on their faces, in fact; their gearboxes and disconnects have very short lives, and in the case of the Thielert engine, necessitated a time before replacement rating (not a time between overhauls) for the entire powerplant unit. Just reiterating what's been said already; in order for them to be successful, aircraft engines need to be designed and built specifically for the purpose...anything else is just too compromised. The problem is that the market for such an engine is so small (maybe only a couple thousand units per year at best) that it's just not worth pursuing. MrChips fucked around with this message at 08:23 on Aug 3, 2015 |
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Aug 3, 2015 08:19
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Hadlock posted:The light aviation engine industry is probably long overdue for a big shake up. This is going to happen in the form of electric propulsion. It will be a while yet, but it is inevitable.
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Aug 3, 2015 08:54
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Why have wankel rotary engines never really taken off in GA? They are very light and compact for their comparative power output, have no reciprocating parts and fewer moving parts full stop. The only drawback is that they have to operate at higher RPM so always need to be geared, but apart from that? Apparently wankels are even better suited for aircraft since they do better if they are operated at a continuous high RPM, as well as by people who are better trained and (generally) know what they are doing. More so than the average shithead car owner anyway.
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Aug 3, 2015 09:23
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Tsuru posted:Why have wankel rotary engines never really taken off in GA? They are very light and compact for their comparative power output, have no reciprocating parts and fewer moving parts full stop. The only drawback is that they have to operate at higher RPM so always need to be geared, but apart from that? Apparently wankels are even better suited for aircraft since they do better if they are operated at a continuous high RPM, as well as by people who are better trained and (generally) know what they are doing. More so than the average shithead car owner anyway. Probably the bad fuel economy and reduction gearing is still required. Edit: Or is fuel economy not an issue at constant RPM for Rotaries?  http://www.rotaryeng.net/
Bondematt fucked around with this message at 09:46 on Aug 3, 2015 |
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Aug 3, 2015 09:38
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Aug 3, 2015 14:37
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Bondematt posted:Probably the bad fuel economy and reduction gearing is still required. I've spent more time than I'll admit researching putting a rotary in to an experimental. The engines themselves run great and hold up to the task beautifully, have comparable fuel burns to certified engines of similar power, and cost around $500 total to overhaul. The downsides are again, the gear drive units. Prone to failure, sometimes catastrophic from odd harmonics between the rotary and the prop, and lack any reasonable way to use a constant speed prop. In the end after pricing everything out over the long term and dealing with any oddities that would for sure pop up in the process, it'd be cheaper, more reliable, less stressful, and easier, to just buy a high time IO-whatever and overhaul it myself. Because let's be honest, anyone seriously entertaining the idea of putting an automotive engine in an EAB is probably more than mechanically inclined enough to overhaul an engine themselves. edit: oh yeah, and rotaries are comically, soul shatteringly, unbelievably loud p.p.s. If you manage to affordably solve the noise and gear reduction problem you'd be well on your way to making a large fortune into a small one. The people that have put rotaries in say they are almost turbine smooth. e.pilot fucked around with this message at 17:37 on Aug 3, 2015 |
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Aug 3, 2015 16:57
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I wish I had the requisite skills to become an A&P but I'd be basically starting at zero. Like, I could maybe manage to do a brake change on a domestic car without watching youtube videos or reading a Haynes manual or something. I changed the oil in my plane once (and was very proud of myself for it) but now it has a spin-on oil filter which means safety wire and I don't know how to deal with that. Bleh.
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Aug 3, 2015 17:17
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e.pilot posted:
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Aug 3, 2015 17:41
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Tsuru posted:Why is it not possible to use a constant speed prop with a wankel? Lack of sufficient engine oil pressure supply? No one makes a gear drive that I could find that supports the mounting of a governor and requisite oil passages. The drawbacks almost always come back to the gear drive unfortunately.
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Aug 3, 2015 18:10
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Hey, look, a new patent for a new Mach 4.5 Airbus that uses a combination of turbojets, ramjets, and a rocket engine. If this actually becomes a Thing, can commercial pilots then say that they do rocket science for a living?
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Aug 3, 2015 19:03
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Nope.
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Aug 3, 2015 19:08
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Looks like something straight out of KSP. We all think it'd be awesome to actually see happen, but it'll never get past that concept image.
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Aug 3, 2015 19:10
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I've always wondered if there was a market for a ~200HP turbo prop engine. I know they make them for R/C airplanes but I have no idea if they would be a feasible replacement for something like an o-360.
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Aug 4, 2015 00:48
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KodiakRS posted:I've always wondered if there was a market for a ~200HP turbo prop engine. I know they make them for R/C airplanes but I have no idea if they would be a feasible replacement for something like an o-360. If you want a higher TBO engine with like double the fuel burn, then yes.
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Aug 4, 2015 00:56
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KodiakRS posted:I've always wondered if there was a market for a ~200HP turbo prop engine. I know they make them for R/C airplanes but I have no idea if they would be a feasible replacement for something like an o-360. Turdoplops just aren't efficient enough at bug smashing altitudes unfortunately.
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Aug 4, 2015 01:10
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e.pilot posted:Turdoplops just aren't efficient enough at bug smashing altitudes unfortunately. Would there be a niche for Lancair style aircraft? Because I would be pretty hot for a lower cost Lancair cruiser.
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Aug 4, 2015 01:32
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CBJamo posted:Would there be a niche for Lancair style aircraft? Because I would be pretty hot for a lower cost Lancair cruiser. Possibly, but then you're talking a niche of a niche. You could spend all that money developing an engine and sell maybe 2. The Lancair IV-P propjet is about as close to that as you'd get at a reasonable price, used they go for about the cost of a new 172 and occasionally dip in to the low $300k range. They are legitimately comparable to CRJ-200 performance in speed though. Edit: Someone needs to make an electric aircraft that uses an APU to power the electric motor just to be as obtuse as possible. e.pilot fucked around with this message at 01:56 on Aug 4, 2015 |
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Aug 4, 2015 01:54
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Wasn't the RR300/RR500 supposed to be a replacement for midrange piston engines? I've seen a few centurions and the like with those conversions installed.
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Aug 4, 2015 05:59
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Butt Reactor posted:Wasn't the RR300/RR500 supposed to be a replacement for midrange piston engines? I've seen a few centurions and the like with those conversions installed. Sort of; they're both derivatives of the Allison/Rolls 250, with the RR300 being much simpler than either the RR500 or the original 250, while the RR500 is basically just the 250 modernised. Both engines were intended primarily for helicopter use, but there have been a few conversions here and there in fixed-wing aircraft. The problem with turbine engines is that they really don't scale well, both in terms of cost and in efficiency. A small turbine engine will always be far more expensive and far less efficient than a piston engine of comparable power output, and the laws of physics dictate that it will likely never change...Reynolds numbers are a bitch.
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Aug 4, 2015 07:21
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What are the best choices for kit planes that are not too hard to build for an amateur, but will also sell for a decent profit when complete?
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Aug 4, 2015 09:10
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DNova posted:What are the best choices for kit planes that are not too hard to build for an amateur, but will also sell for a decent profit when complete? Vans.
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Aug 4, 2015 12:31
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CBJSprague24 posted:RAH is going to be cutting flying commitments through the first half of 2016: http://www.skywriteraviation.aero/2015/07/27/the-us-pilot-shortages-first-victim-republic-airways/ I thought of this post while I sat in a Republic-paid Indianapolis hotel room stranded Sunday night by a cancelled flight due to no crew. With the next flight with open seats being the next morning. As a passenger I want Republic to do well since they fly the Embraers that are so much better comfort-wise than the CRJs Air Wisconsin flies.
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Aug 4, 2015 13:49
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As a passenger I also want my pilots to earn enough to not be worried about whether they're going to be able to pay their mortgage or medical bills. At least Air Wisconsin pays a living wage after year 1. Two Kings fucked around with this message at 14:42 on Aug 4, 2015 |
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Aug 4, 2015 14:36
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Two Kings posted:As a passenger I also want my pilots to earn enough to not be worried about whether they're going to be able to pay their mortgage or medical bills. You can sleep in a plane but can your house fly? I think not. 
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Aug 4, 2015 14:48
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As a Canadian, I just want to apologize again for the horror that is the passenger experience on a CRJ. God, those things are loving uncomfortable. Are they any better from a pilot's perspective, at least compared to alternatives?
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Aug 4, 2015 14:49
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hobbesmaster posted:You can sleep in a plane but can your house fly? I think not.  When???
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Aug 4, 2015 14:50
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Two Kings posted:As a passenger I also want my pilots to earn enough to not be worried about whether they're going to be able to pay their mortgage or medical bills. I'm ok with Air Wisconsin doing well too; the CFI who trained me for my private pilot certificate is a FO there. But that's still not enough to get me to fly in the back of a CRJ. edit: actually, just saw on FB my CFI just made captain. Still not willingly flying in the back of a CRJ though. fordan fucked around with this message at 15:09 on Aug 4, 2015 |
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Aug 4, 2015 15:03
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PT6A posted:As a Canadian, I just want to apologize again for the horror that is the passenger experience on a CRJ. God, those things are loving uncomfortable. Are they any better from a pilot's perspective, at least compared to alternatives? I think the 900 is a fine airplane. It's got plenty of power to climb and it cruises faster than the Ejets, which is nice if its the last flight on gone home day. It's a real airliner. I haven't flow the 200 but I hear it's a dog. Some guys that have flown both preferred the way the 200 handled. More like a sports car than the 900, which is like driving a freight truck.
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Aug 4, 2015 15:15
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CRJ-200s can gently caress off, forever.
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Aug 4, 2015 15:47
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I've flown CRJ-200/700/900. The CRJ-700/900 is like a Mercedez Benz compared to the CRJ-200 (a beat up 97' Camry). The CRJ-200 is not only underpowered, the engines are optimized for lower altitudes, so it climbs and performs like poo poo. It has no FADEC to control the engines so you manually have to adjust them, constantly compensating for asymmetric thrust just like you would on a prop plane. Systems such as hydraulic controls make no sense. As far as the passengers, the CRJ-700/900 has MUCH better air conditioning which makes a huge difference in the summer. I almost stood up and walked away from an Endeavor CRJ-200 last summer during a deadhead, it had a broken pack and I was about to pass out as we waited and waited for push-back. Also two lavatories on the 900 which can be important to some people. The passenger windows are reasonably located in the CRJ-700/900(seriously, who thought of putting the windows down to your elbow level on the CRJ-200?). Seating can be more comfortable depending on your airline's configuration. In short, the CRJ-200 is trash and needs to be retired. Animal fucked around with this message at 16:32 on Aug 4, 2015 |
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Aug 4, 2015 16:30
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