Radial Engines vs Inline Engines?

[earl1937]

Ta-152 has an inline engine and I believe it hit the highest altitude of the war.

Edit: Earl is talking about climb rate?

Climb rate had nothing to do with their decision, it was all about what could accelerate from "zero" to 80 knots in the shortest distance, which is the speed at which the early fighters became airborne. Most of all the "by-winged" early fighters could fly at 60 knots and even they had radial engines. Of course, we must remember that after the carrier turned into the wind, the aircraft had anywhere from a 40 knot to 60 knot headwind, before they started their roll down the carrier.
I have often wondered what the B-17 performance would have been, with the Avro Lancaster engines installed on it! Any comments on that question?

[DaveBB]

They tried it.  I'm not sure what the performance results were though:

[WaffenVW]

I don't know about the performance, but that thing is just gorgeous.

[WaffenVW]

And those are turbo-supercharged Allisons I believe, not the Merlins of a Lancaster.

[Randy1]

Interesting replies.   I greatly appreciate the information.  It was one of those questions you ponder for a bit then just had to ask.

After reading all the replies I wondered if radial engines had been tried in cars.  Do a Google on "radial engine cars."  Some real neat images.  Too many to post.

[DaveBB]

General characteristics

Crew: 10
Length: 74 ft 0 in (22.56 m)
Wingspan: 103 ft 11 in (31.67 m)
Height: 19 ft 2 in (5.84 m)
Wing area: 1,420 ft² (131.9 m²)
Empty weight: 34,750 lb (15,762 kg)
Loaded weight: 56,000 lb (25,401 kg)
Max. takeoff weight: 64,000 lb (29,030 kg)
Powerplant: 4 × Allison V-1710-97 turbosupercharged liquid-cooled V12 engines, 1,425 hp (1,063 kW) each

Performance
Maximum speed: 327 mph (284 knots, 526 km/h)
Cruise speed: 226 mph (197 knots, 364 km/h)
Range: 3,300 mi (2,870 nmi, 5,310 km)
Service ceiling: 29,600 ft (9,020 m)

The work for this project was handed over to Lockheed’s Vega subsidiary who were already building B-17’s at the time. When the prototype flew it showed improved performance over the standard radial engines.  The B-38 was 40mph an hour faster then the standard B-17.

[WaffenVW]

I love the radiator placement between the engine nacelles.

[Randy1]

I would have suspected a notable increase in fuselage length with the forward weight shift.

[WaffenVW]

Not on such a big bird. Could probably compensate by moving some internal equipment like oxygen bottles etc. back in the rear fuselage.

[earl1937]

I would have suspected a notable increase in fuselage length with the forward weight shift.

The "moment" arm would have more than compensated for the additional weight, by placing a, for example, a 72 inch "plug" between the end of the dosal fin and the bomb bay rear bulk head! I am not sure what the length of travel of the C.G. is on the 17, Columbo could tell us I suppose, but with a plug like I describe, I doubt if it would increase the travel distance enough to make much difference in figuring weight and balance.

[Charge]

In radial engine the cooling opening itself causes comparatively small drag increase to that of an inline cowling but the drag rises if a vent in opened behind the engine to vent the hot air. If you look at the early 190s they had no vents what so ever except the holes for exhaust stacks. Later on there were cooling louvers added in back of the engine mount to assist cooling the engine accessories. The fan added the forced circulation of air inside the cowling so that the needed venting remained low if you compare it to eg. that of Corsair which had ample venting for the engine.

The cylinder weight is also higher since the heat transfer to air is less efficient than transferring the heat to coolant causing the radial to have more "cooling weight" compared to inline engines.

-C+

[WaffenVW]

Regardless of cooling drag the wider fuselage required for a radial engine application increases form drag considerably.

[Ack-Ack]

The work for this project was handed over to Lockheed’s Vega subsidiary who were already building B-17’s at the time. When the prototype flew it showed improved performance over the standard radial engines.  The B-38 was 40mph an hour faster then the standard B-17.

The XB-38 only showed improvements in its higher speed over the B-17 but at the cost of a lower service ceiling.

[WaffenVW]

How much lower?

[Oldman731]

How much lower?

Wiki puts the XB-38's service ceiling at 29,600 feet, and the B-17G's at 35,600 feet.  The XB-38 only flew nine times, between May and June, 1943, before catching fire and crashing.

https://en.wikipedia.org/wiki/Boeing_XB-38_Flying_Fortress#Specifications_.28XB-38.29

https://en.wikipedia.org/wiki/Boeing_B-17_Flying_Fortress#Specifications_.28B-17G.29

- oldman