Why does the PA-38 Tomahawk have a wing life of 11,000 hours?
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I'm afraid we'll see a lot more of this in the future. There are a number of SID's (Supplemental Inspection Documents) in the works for Cessnas. They will start with the oldest and least supported models, like the 336 and the 337 Skymaster but will most certainly migrate to the older singles as well soon after. Cessna do not want to be responsible for old aircraft falling out of the sky. Plus, it doesn't hurt sales either.
Now, in FAA-land for part 91 operations (private flying), this inspection is voluntary. For part 135 it's not. In EASA-land you can bet they will be mandatory for all, so that will overnight make any Skymaster on the European register worthless (as the inspection is north of $60K).
I myself as an Aero Commander owner am in a similar bracket. I happen to own one of the few models in their range that doesn't have a wing inspection AD, but most of the models between the early 60's and 70's had this. There were some accidents due to a combination of cold extrusion of the main spar and galvanic corrosion from a strap. Now, with the spar modification in place, the AD goes away and many Commanders soldier on (still) with almost 20.000hrs on them (I know an operator with 30 of them, who regularly flies them beyond 15.000hrs).
But ultimately, and as I fly an aircraft from 1953 myself, one can't help to sometimes think about the structural integrity of an almost 60 year old wing. I certainly do. That's why I really ask them to check extra carefully for any type of corrosion or funny spots during my annual. But I'm also calmed by the fact that they many times overbuilt things back in those days, so everything just feels a little beefier.
Now, in FAA-land for part 91 operations (private flying), this inspection is voluntary. For part 135 it's not. In EASA-land you can bet they will be mandatory for all, so that will overnight make any Skymaster on the European register worthless (as the inspection is north of $60K).
I myself as an Aero Commander owner am in a similar bracket. I happen to own one of the few models in their range that doesn't have a wing inspection AD, but most of the models between the early 60's and 70's had this. There were some accidents due to a combination of cold extrusion of the main spar and galvanic corrosion from a strap. Now, with the spar modification in place, the AD goes away and many Commanders soldier on (still) with almost 20.000hrs on them (I know an operator with 30 of them, who regularly flies them beyond 15.000hrs).
But ultimately, and as I fly an aircraft from 1953 myself, one can't help to sometimes think about the structural integrity of an almost 60 year old wing. I certainly do. That's why I really ask them to check extra carefully for any type of corrosion or funny spots during my annual. But I'm also calmed by the fact that they many times overbuilt things back in those days, so everything just feels a little beefier.
It is kind of crazy that tomahawks are still flying now, 30+ years after being built, I'm sure surpassing all expectations of those who made them.
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Plus, metal is easily inspected and repaired. Imagine years down the line when these old S-glass or composites have been flying for 50 years - nobody knows what lurks within those structures after such a long time. We have it good - it's only going to get worse.
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I have a spare set of fabric covered wings
I don't know...
Older aircraft and engines are hugely inefficient compared to some of the newer types. I doubt if avgas/mogas are ever going to get cheap again and I expect this is going to get ever more important.
Secondly, aviation infrastructure is expensive - if it isn't well utilised, it's going to disappear.
Older aircraft and engines are hugely inefficient compared to some of the newer types. I doubt if avgas/mogas are ever going to get cheap again and I expect this is going to get ever more important.
Secondly, aviation infrastructure is expensive - if it isn't well utilised, it's going to disappear.
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It depends very much on what you want to do. I certainly wouldn't say they were "massively" inefficient. I have a 1952 C90 cub that does 18 l/h but doesn't go very far, it doesn't go as fast as a SportCruiser but it was also less than 1/5th the cost and wont depreciate, at all. Whereas the sportcruiser will depreciate by half over about 10 years. To get that money back I would have to do a boatload of hours. I can fix just about anything in my cub for relatively little money, the same cannot be said for the "more efficient" modern aircraft you talk about 
.
I'm not saying they're not good, they are. But it's a blinkered opinion that the old stuff is worn out and expensive to run. It's not by a long shot.
The Tommie is even better, you can buy a servicable one for about £7k it burns 23 l/h of AVGAS and will take all the ****e that Ab initio training will throw at it without failing anything too expensive (except the bastard noseleg). It pays for itself in a matter of months.
Flying fast, for little fuel is only a portion of the game and while it's relevant it's not for training, which is the Tomahawks only mission, because PPL training is about the time you spend in the air, not how far/fast you go.
It will only be replaced when there is a hardy fuel efficient and cost effective alternative. The AT3, SportCruiser, Remos GX, SkyCatcher, are neither tough nor cheap and that is why we will see people training on PA28s from '76 and C172N/Ms for years to come.
.I'm not saying they're not good, they are. But it's a blinkered opinion that the old stuff is worn out and expensive to run. It's not by a long shot.
The Tommie is even better, you can buy a servicable one for about £7k it burns 23 l/h of AVGAS and will take all the ****e that Ab initio training will throw at it without failing anything too expensive (except the bastard noseleg). It pays for itself in a matter of months.
Flying fast, for little fuel is only a portion of the game and while it's relevant it's not for training, which is the Tomahawks only mission, because PPL training is about the time you spend in the air, not how far/fast you go.
It will only be replaced when there is a hardy fuel efficient and cost effective alternative. The AT3, SportCruiser, Remos GX, SkyCatcher, are neither tough nor cheap and that is why we will see people training on PA28s from '76 and C172N/Ms for years to come.
I don't disagree with anything that Dan's said... And I never meant to imply that old aircraft were bad aircraft. However they were designed in different times - generally before the oil embargoes and concerns about global warming, and before ordinary Chinese started to buy cars.
Fuel already makes up about half of the Tommie's running costs (in the UK), and they certainly do seem to need a lot of maintenance. If fuel prices were to double... triple... quadruple... then older aircraft would become less and less economical.
I obviously don't know whether this will come to pass, but I wouldn't be surprised if it happens within the decade. If so, then I reckon it will be devastating for GA and particularly gas-guzzling types.
Also, is efficiency really mutually exclusive with durability? Many of the newer types have been heroically squeezed into the weight limits set by microlight or LSA specifications, and it strikes me that this may be a more fundamental reason why they tend to be flimsy in some respects (e.g. nosewheels). As Silvaire points out, there are plenty of old LongEZs about, so composite aircraft can be reasonably durable.
Anyway, the long and short is that I could already rent a C42 for an hour wet, for less than the price of an hour's fuel in a Tomahawk. I'm going to try it as soon as I get my PPL, and see how I get on with the aircraft. Perhaps I'll find it doesn't suit me.
Fuel already makes up about half of the Tommie's running costs (in the UK), and they certainly do seem to need a lot of maintenance. If fuel prices were to double... triple... quadruple... then older aircraft would become less and less economical.
I obviously don't know whether this will come to pass, but I wouldn't be surprised if it happens within the decade. If so, then I reckon it will be devastating for GA and particularly gas-guzzling types.
Also, is efficiency really mutually exclusive with durability? Many of the newer types have been heroically squeezed into the weight limits set by microlight or LSA specifications, and it strikes me that this may be a more fundamental reason why they tend to be flimsy in some respects (e.g. nosewheels). As Silvaire points out, there are plenty of old LongEZs about, so composite aircraft can be reasonably durable.
Anyway, the long and short is that I could already rent a C42 for an hour wet, for less than the price of an hour's fuel in a Tomahawk. I'm going to try it as soon as I get my PPL, and see how I get on with the aircraft. Perhaps I'll find it doesn't suit me.
Well, there's something special about the LongEZ. I grew up reading about them in the national geographical. Always wanted one. May get one, but not for a while yet...
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As regards efficiency, there has never been and never will be a free lunch - all the time you are burning hydrocarbons to get propulsion.
The old Lyco engines, when in cruise and running at peak EGT (stochiometric), are as efficient as the most modern car engines when running in similar conditions e.g. going down the motorway at 80mph.
Similarly there is no possible significant difference between a Lyco and a Rotax. The Rotax should benefit from a more modern combustion chamber design, etc, but it loses out by running at a high RPM which, as every Lyco owner with a VP prop and some decent instrumentation will know, is a great MPG killer.
The way to make a plane do more MPG is... wait for it ... to make it smaller
Reduce the cockpit volume and you get better MPG. Especially if you make it a tandem design so the cross section is small.
The PA38 probably does more or less the same MPG as any other plane with that size cockpit and the same or similar engine.
The total operating costs of a plane are not just the fuel, of course. Once an aluminium airframe goes past 10-20 years (depending on whether hangared, abused, etc) then you have to start replacing airframe parts, and these are universally expensive.
The reason every PA38 is a knackered old heap is because they are all around 30 years old and most of them were kicked around the flying school scene. I started my PPL in them and the ones I used to fly were the worst bits of crap ever, with an inch of water on the cockpit floor following a rainy night, stunk like a public phone box, one would drain about half a litre of water out of the tanks following some rain (perished filler cap seals), the trim was knackered, the yoke was just bare metal rusted up with decades of students' sweat (and everybody flying a PA38 seems to be constantly sweating because it gets hot and most of them are flying circuits ).
Very few people bought PA38s for private flying because it is not really suitable for going anywhere. It is too agile to give you any rest.
The old Lyco engines, when in cruise and running at peak EGT (stochiometric), are as efficient as the most modern car engines when running in similar conditions e.g. going down the motorway at 80mph.
Similarly there is no possible significant difference between a Lyco and a Rotax. The Rotax should benefit from a more modern combustion chamber design, etc, but it loses out by running at a high RPM which, as every Lyco owner with a VP prop and some decent instrumentation will know, is a great MPG killer.
The way to make a plane do more MPG is... wait for it ... to make it smaller
Reduce the cockpit volume and you get better MPG. Especially if you make it a tandem design so the cross section is small.
The PA38 probably does more or less the same MPG as any other plane with that size cockpit and the same or similar engine.
The total operating costs of a plane are not just the fuel, of course. Once an aluminium airframe goes past 10-20 years (depending on whether hangared, abused, etc) then you have to start replacing airframe parts, and these are universally expensive.
The reason every PA38 is a knackered old heap is because they are all around 30 years old and most of them were kicked around the flying school scene. I started my PPL in them and the ones I used to fly were the worst bits of crap ever, with an inch of water on the cockpit floor following a rainy night, stunk like a public phone box, one would drain about half a litre of water out of the tanks following some rain (perished filler cap seals), the trim was knackered, the yoke was just bare metal rusted up with decades of students' sweat (and everybody flying a PA38 seems to be constantly sweating because it gets hot and most of them are flying circuits
).Very few people bought PA38s for private flying because it is not really suitable for going anywhere. It is too agile to give you any rest.
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"Similarly there is no possible significant difference between a Lyco and a Rotax"
So why does the AT-3 need 14 litres of fuel to top up after an hours instruction and the PA-38 needs 22 litres then?
So why does the AT-3 need 14 litres of fuel to top up after an hours instruction and the PA-38 needs 22 litres then?
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It is too agile to give you any rest.
I will admit I had over 10's of flights altered the trimming tabs so they were spot on for cruise. It just takes a bit of effort by a pilot and they just as good as anything else for flying in a striaght line.
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The AT3 is lighter, more aerodynamic but nowhere near as tough, it also has more frequent and expensive tech issues. Not to mention being £100k to buy.
It's a good plane but it's been designed for a different job, not to mention that it needs full rudder on the take off roll in zero wind, which is wholly unacceptable for a trainer.
the CT and the C42 are the same except that they're microlights, so only good for NPPL (M) and PPL (M).
Those flying schools I spoke to that have been using the AT3 in anger, wish they weren't for the above reasons.
Mission is key. You can't compare apples and cucumbers or oranges with potatoes 
It's a good plane but it's been designed for a different job, not to mention that it needs full rudder on the take off roll in zero wind, which is wholly unacceptable for a trainer.
the CT and the C42 are the same except that they're microlights, so only good for NPPL (M) and PPL (M).
Those flying schools I spoke to that have been using the AT3 in anger, wish they weren't for the above reasons.
Mission is key. You can't compare apples and cucumbers
or oranges with potatoes
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needs full rudder on the take off roll in zero wind, which is wholly unacceptable for a trainer.
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Anyway the weegie is going to be flying another tough auld girl in a couple of weeks.
Congratulations of passing your first type rating LST. All those hours in the tommy put to good use. 700kg to 7000kg and 65knts to 130knt approaches in one hop. Oh and it has a limit of 31000 cycles but they have just got an extension up to 42000 cycles
without any mods. Built like a brick ****e house.
Congratulations of passing your first type rating LST. All those hours in the tommy put to good use. 700kg to 7000kg and 65knts to 130knt approaches in one hop. Oh and it has a limit of 31000 cycles but they have just got an extension up to 42000 cycles
without any mods. Built like a brick ****e house.
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needs full rudder on the take off roll in zero wind, which is wholly unacceptable for a trainer. If true, it's unacceptable for, ahem, flying of any sort, because what if you get some, ahem, wind from the right?
Truely awful design.
The way to make a plane do more MPG is... wait for it ... to make it smaller 
As an example of how older aircraft simply haven't been designed with efficiency in mind, I always wondered at the sharp wing-root junctions on the PA38 and PA28. Sure enough, when I looked for a wing root fairing kit, the manufacturers claimed to increase speed by 2-3 knots - which probably counts for an efficiency increase of 5% or so if you kept the airspeed constant.
I still suspect that many of the drawbacks of the present offerings are due to the microlight and LSA design criteria. They are mandated to have comparatively low stalling speeds, necessitating larger wings. Top speed is limited, so they'll never be able to compete as tourers.
But anyway, where I live my renting options are essentially C42s or PA28s - why would I want to hire a 4 person plane for a solo or 2-person outing, which will make up the majority of my flying over the next few years.
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I don't disagree, but in your list are parameters which alone will give a better MPG by flying slower.
If you have a lower wing loading / a lower stall speed (a requirement on microlights and other "ultralight" stuff) then you end up with a plane whose optimal cruise speed is lower, and that alone will produce a better MPG.
The Long-EZ is a tandem, which will easily be hugely more efficient. It also does away with the elevator drag causes by the elevator pushing down in most traditional designs. Canards are more efficient due to this.
The rest, like wing root fairings, are little details which all help. My TB20 is covered in pop rivets and it's obviously cheaper to do that than flush rivets, and my guess is that Socata didn't think it is worth spending the extra money to get maybe a few extra kt.
It is a known fact that the retractable footsteps on the TB20GT are worth an extra ~2kt; Socata apparently did that to preserve the POH performance figures despite the taller roof, because any change to the POH creates a lot more certification work
Aerials can make a big difference too. If you have 2 x VHF, ADF, DME, XPD, that is probably 3kt down the drain.
If you have a lower wing loading / a lower stall speed (a requirement on microlights and other "ultralight" stuff) then you end up with a plane whose optimal cruise speed is lower, and that alone will produce a better MPG.
The Long-EZ is a tandem, which will easily be hugely more efficient. It also does away with the elevator drag causes by the elevator pushing down in most traditional designs. Canards are more efficient due to this.
The rest, like wing root fairings, are little details which all help. My TB20 is covered in pop rivets and it's obviously cheaper to do that than flush rivets, and my guess is that Socata didn't think it is worth spending the extra money to get maybe a few extra kt.
It is a known fact that the retractable footsteps on the TB20GT are worth an extra ~2kt; Socata apparently did that to preserve the POH performance figures despite the taller roof, because any change to the POH creates a lot more certification work
Aerials can make a big difference too. If you have 2 x VHF, ADF, DME, XPD, that is probably 3kt down the drain.
It also does away with the elevator drag causes by the elevator pushing down in most traditional designs. Canards are more efficient due to this.
It's apparently not always true either that tandem seating is more efficient than side-by-side seating ('sociable', to borrow cycling terminology). What tandem seating loses in x-sectional area, it makes up for in wetted area. On the Long-EZ this is 'free' because the passenger is effectively sitting where the empennage would otherwise be, and this space is poorly utilised in most aircraft.
Other than that, I don't think we're disagreeing so much on matters of fact as emphasis. And perhaps not even on that - I agree that the best way to massively reduce an aircraft's consumption is to make it much smaller, but I don't agree that the rest's just icing.
Touring motor gliders (and derivatives) are another class of aircraft with a l/d at least twice that of most light aircraft. Again, most of them aren't designed to go fast, but when compared with aircraft in the same speed category (like the Tommie) they still come out very favourably in terms of fuel consumption.