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Why is it radial engines aren't around?

Jenny S

Registered User
What is it they're not used much these days outside of historic craft, but inline piston engines are?

Is it that the radials now fall into a place where they make more power than inline piston engines, but with so much weight it's more efficient to use turbines for the same applications now? Or do they produce about the same amount of power at about the same amount of weight as the inline engines, but with more complexity and timing issues?

Or something else?
 
way more parts to make them operate and don't have the reliability/ engine life of a good opposed.( not that many inline aircraft engines either mostly apposed) They are still used in Ag aircraft quite a bit, but they are used 60 yr old engines.
 
I was under the impression that at least the R985 is more reliable than the continental's and lycoming's.

I think some reasons for their not being around on US planes are a) they aren't very easy on the coefficient of drag on planes; and b) they are thirsty - plus who makes them anymore outside eastern europe?
 
I just finished overhauling two cylinders for a 220 Continental on the Stearman. The 220 is a major pain in the butt to work on compared to horizontally opposed engines.
JimC
 
The big radials in airline operations had @7000 hr. TBOs. Of course this was done in the 40's and 50's, on long legs typically, and high octane fuels.
 
I don't think its a tbo issue. Even the R-985 now has a respectable tbo, compared to some flat engines (compare to a Cont. IO 360, for example) and they can get there. Since there are no new ones and lots of parts, they're relatively cheap to overhaul.

The physical size and shape of the engine really dictates aircraft appearance and, as mentioned, DRAG. Also, the reason the oil tank in a Beaver sits between the pilot's and copilot's knees is to get the CG within range--They are pretty heavy, but if you need the power.....

I'm not sure when the last radial was built by P & W, but I'll bet it was in the early 50's. Anyone know for sure?

For an airplane which justifies the power that a radial can deliver, a turbine is at least almost practical, and a LOT lighter, and even more powerful.

Also, radials require a lot of specific care and feeding, and they don't brook abuse by ham fisted pilots very well. Abuse will result in higher maintenance costs, not necessarily catastrophic failure. While a small turbine has a similar caveat (except with abuse they CAN implode), they are "warmed up" as soon as they're up to speed, whereas a radial really needs to thoroughly warm up prior to making all that power. And, pilots are always in a hurry to launch....

MTV
 
But the sound is like nothing else.

Brother Dan flew over my place the other day in the Stearman; I heard him coming long before he arrived. The ag-planes this summer were pretty nice to hear as well.

Turbines are nice but man, oh man, the fuel burn at low levels... Dan's 220 probably burns 13 per hour; the smaller turbines (what, 350shp?) would likely double that.

Jon B.
 
MTV,

I have had to sit at idle with a turbine quiet a few times waiting on temps to rise and stabilize. Turbines can be unforgiving of the porky handed pilot too.

I would say radials fill a gap between the 300/350 class pistons and the 420hp turbines, granted that gap is very, very limited. Maybe a Russian aerobatic plane, a few "novelty" aircraft. Lack av-gas may be the ultimate stake through the heart of piston engines. Piston/prop engines are still the most efficient way to power airplanes.
 
Yeah, I figured someone would jump on me about that, but I did note that turbines can come unglued with the wrong operator as well.

Not disagreeing with you, but it's a matter of degree ( 8) ). On a first start of the day, a good 10 to 15 minute warm up makes a radial happy. Turbines shouldn't really need THAT long.

Shoving the go-lever hard forward in ANY engine is less than desireable.

MTV
 
On the Beaver, they had to extend the plane (in an ugly manner too) to get the extra fuel they needed for the turbine. Unless you do what Wip does and put it in the wings, which doesn't make it as fun to fly.

And without pressurization, you get that horrible smell when taxiing.

Nothing like the sound of a radial engine, and as Mike says, they are very inexpensive, relatively, to overhaul.

There is no set TBO for them btw. There are guidelines, but figure 1,600 hours or so?
 
btw, here is an old post talking from a mechanic talking about the overhaul on the r985:

> Was wondering what the cost to maintain a radial is compared to a
> typical Lyc or Cont engine. What is typical TBO for a Pratt R-985 from
> an SNJ? What is the cost to overhaul? I know of one place (Covington)
> that specializes in radials, but that's gotta be a pain to ship an
> engine to their shop. Can any maint. shop overhaul a radial, or is
>that
> best left to specialists? Except for the fuel burn, are operating
>costs
> similar between radials and pancake engines?
snip

For every R-985-AN-14B (rated at 450 hp continuous) I've changed at
1500 hrs, I've had to yank one somewhere around 1,200. I've also seen a
couple spit off cylinders, and one had some sort of massive rod failure
(I couldn't tell exactly what went wrong, the cylinder skirts were
peened over and wouldn't come out of the case).

You can get a decent overhaul for around $16-18,000 (to overhaul your
intact run-out engine). But as the N# dude mentioned, if you need a
crank the price goes waaaay up. You crate them up and ship them like
any other engine, a lot of trucking companies will give you a break on
freight if you code it right. There are quite a few guys around that
will still overhaul them.

If you want to find the "best" deal, find an aerial applicator with an
Ag-Cat or a round-engined Air Tractor-I can guarantee you that he has
not only shopped around, but has gotten the low-down from all his crop-
dusting buddies.

Direct operating costs can be tough to figure, but they are going to be
similiar to a boxer engine. To get one to TBO, you can plan on going
through around 650 gallons of oil and around 45,000 gallons of gas. You
need to set the valves at least every 400 hours, and it's a good idea
to re-torque the cylinder base nuts every 500 hours. You'll go through
around 75-80 massive electrode spark plugs, or maybe 35 fine-wire's
(depending how many you drop).

Figure in 2 magneto overhauls, plus probably 3 cracked jugs. If you
only use the 450 ponies when you have to, you might get by with 2-if
you like to make it roar, plan on 4-5. If you can find low-cycle jugs
(good luck) you might get off with 1 (or none). If you keep the valves
adjusted and the rockers in good shape, plan on yanking 2 to get the
valves/seats ground. Exchange jugs used to be relatively cheap and
plentiful, but it's been 10 years since I had to shop for any.

Back when I was workin on 'em there wasn't a real good aftermarket
external oil filter kit, now there are several. I would think that an
oil filter (instead of a screen) would make a big difference in making
it to TBO.

Bearing in mind that you're talking about an integrally supercharged
engine, the fuel burn-to-hp really isn't as bad as what you might think.

Oh, if you keep your bird in an un-heated hangar in a moderate climate,
plan on having to dry out the ignition harness at least a couple of
times in the spring and in the fall. You either have to loosen all the
nuts and heat the crap out of it, or flush out the water with a
dielectric.

These numbers are based on maintenance I've performed in the course of
about 25,000 flight hours on relatively well-maintained "working" Super
18's. That includes 3 catastrophic in-flights (all over 1,000 hrs SMOH,
and all with un-eventful on-airport landings-no engine fires).
 
I think that should be an R1340 on the SNJ.

The majority of the rod failures I have seen on radials were from hydraulic lock. Had to cut the bottom two rods off to get the cylinders off. :eek: Can't beat the sound of those old radials. Jim, I bet after you customize a bunch of your tools they will be easier to work on. :lol:
 
radial engine

A well known advantage of running a radial engine is that your airframe is unlikely to ever rust because of the even distribution of an oil coating!
 
I've seen R-985s bring home their pilots with some pretty amazing damage to the engine. If well cared for, they work good, last a long time, and make plenty of power. Just don't think you can run them like a Lycoming.

MTV
 
I work on two Ag Aircraft running the R985 radial and I really like them, once you get a good one, its not hard to keep the leaks down, keep it adjusted and pretty maintenance free. but for power you have to burn fuel an average of around 32 gals per hour. good engines though. :drinking:
 
Man, they must be running a LOT of power:eek:. Fuel burn for a Beaver on floats runs around 22 gph. Not fast, but pushing it up to 30 gains you about a half a knot :angel: .

MTV
 
The key to leak prevention is like jobadias says... keep after them. We also checked all the gasket surfaces with a straightedge and lapped quite a few, then used Loctite #510 & 518. I used to travel around with a Fairchild that had one of the engines I did, and I'd usually sit under it in my lawnchair at the shows...sure had alot of folks figure I was going to get "oiled".... but seldom was.
MTV's right on... everyone's in too much of a rush anymore to run a round engine right... they take some time to warm up and to cool down. The really good operators didn't have much problem, but the guys that were in a rush or believed too many stories, usually didn't have such great service. It amazed me to work in the overhaul shop in teardown, and see the difference in the condition of the engines that came in.
JH
 
My Dad told me that some of the Sherman tanks used a radial aircraft engine (R-985 ???). He was with a tank maintenance outfit in Patton's 2nd Armored Division. Apparently Christmas Eve, 1944 wasn't too much fun, as he and his buddy Marvin had to change plugs on one up on the front to get it running. Every time they used a flashlight to try and see what they were doing,...the German's would shoot at them !!!!!

Jim
 
55-PA18A said:
My Dad told me that some of the Sherman tanks used a radial aircraft engine (R-985 ???). He was with a tank maintenance outfit in Patton's 2nd Armored Division. Apparently Christmas Eve, 1944 wasn't too much fun, as he and his buddy Marvin had to change plugs on one up on the front to get it running. Every time they used a flashlight to try and see what they were doing,...the German's would shoot at them !!!!!

Jim

I believe they used the Continental W670-9A Tank engine, very similar to the aircraft version. except different accessory case. the Cylinders were the same, you can tell the difference between old tank jugs and aircraft jugs by being able to see 2 stud holes on the front of the cylinder.
The old Sikorsky helicopter used 1340 radial engines too!
 
mghallen said:
The big radials in airline operations had @7000 hr. TBOs. Of course this was done in the 40's and 50's, on long legs typically, and high octane fuels.

I think that you may be misinformed. I think that we're somewhere around 24-2500 hours TBO on the R-2800, and that is with some extensions.

United, when it was operating DC-6 used to do a top overhaul every 1000 hours. Not sure how long they went on a bottom end, but I'd be pretty surprised if it was anywhere near 7000 hours.
 
...used to be , back in the 80's, and we bought a couple of the first turbines in our area. you heard turbine ag plane working,you had to go see who it was.
2day, you hear a round motor working, you gotta drop everything to go see who/what it is :p .
as far as reliability goes, i think it's a matter of maintenance practices, operating practices, and who did the overhaul.
i miss the old round motors, got to LISTEN and watch butlers DC-7 go by enroute to a fire and return an hour later. talk about symphony on the wing! that, was BEAUTIFUL!
i fly a pt-6 that is reliable as could ever be(good maintenance).
but there are some i wouldn't touch w/ a10 foot pole.
guys go cheap gettin in and stay cheap trying to operate them.
that's a grenade, pin out.
you want any aircraft engine to last(or airframe), you got to pay the money to keep it right.
i relish every oppurtunity to get back in our round motor, but i'm sure more productive behind my turbine.
one of my competitors still has a 450 ag-cat. glad he's still around.
 
let's not forget.....
we have been running on war surplus parts for a very long time.
that pile has got to be dwindling.
leland snow tried to help out by going into production of 1340 cranks.
didn't work out so well. wound up w/ an A.D. against them.
m's pratt & whitney would probably @&$% a collective gourd if they had any idea that we were still flying behind these things.
actually they were just owners of a civil war cannon foundry. the true name of the real engineer escapes me at the moment.

in case anybody hasn't been looking....that was a (very LARGE,LOUD, pumped up)
round motor that won at reno sunday! YEAH!!!!
 
aalexander said:
mghallen said:
The big radials in airline operations had @7000 hr. TBOs. Of course this was done in the 40's and 50's, on long legs typically, and high octane fuels.

I think that you may be misinformed. I think that we're somewhere around 24-2500 hours TBO on the R-2800, and that is with some extensions.

United, when it was operating DC-6 used to do a top overhaul every 1000 hours. Not sure how long they went on a bottom end, but I'd be pretty surprised if it was anywhere near 7000 hours.


Yeah, checked with one of the big cheeses in the Mx Dept. Current TBO on an R-2800 is 2300 hours and we have a conditional exemption that boosts it over 2400. The TBO when it first came out was 1000 hours and P&W increased it as experience with the engine was gained.
 
Having had the opportunity to fly around in a Wip turbine beaver, I would certainly sacrifice the fuel in the wings for the performance. Although on the water the fuel tends to cause the airplane to rock a little more compared to having the fuel in the belly. The turbine roughly burns 45 gal/hr and cruises about 50 knots faster. If you truly want to fly something fun, Wip is now putting the -34 turbine in which is rated at 750 hp. It is more like flying a helicopter...
 
I really like the looks of the Wip turbine beavers, but I didn't like the fuel in the wings in terms of how they fly. Trade-offs for sure.
 
Yes, the wet wing is not like flying the radial with the belly fuel system. The upside is that for all intents and purposes, it is a copy of a Caravan system. It is not the easiest plane to fuel on the ground either. But, we can accomplish in one trip with the Beaver that would take three trips in a 185. In addition, we can haul ATV's and large cargo that would never fit in the 185.

I think if we did it again we would try the Viking Mod over the wip. I think the wip is better looking, but I like the larger tail in the Viking version as it tracks a hell of a lot better. Unfortunatley, when we were looking to buy, we found the people at Viking to be rather unresponsive. The people at wip have been great. Mark Mathisen is worth his weight in gold!
 
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