A small what-if: Ju 52 with two engines and a retractable U/C instead of the 3-engined layout?

tomo pauk said:

To be frank, I'm okay with the Ju 52 retaining the fixed U/C after all.

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If they could shift to higher powered versions (which may need stronger mounts and a bit if wing reinforcement) You may get close the power of the old 3 engines.
yanking the engine a prop could save you about 1000lbs or more. Extend the fuselage about 3-4 feet so the crew helps restore the CG. Adds 2-4 seats/cargo?
Put a pointy nose on it
Of course if one engine dies the whole plane is going to hit the ground in short order, that things was not going to stay in air on one 1000hp engine.

Shortround6 said:

If they could shift to higher powered versions (which may need stronger mounts and a bit if wing reinforcement) You may get close the power of the old 3 engines.
yanking the engine a prop could save you about 1000lbs or more. Extend the fuselage about 3-4 feet so the crew helps restore the CG. Adds 2-4 seats/cargo?
Put a pointy nose on it

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They IMO must shift to the more powerful 132s - like the circa 900 HP 132 versions, even though the Bramo 323P would've been the best, with it's 2-speed S/C. Granted, 323s were not produced on the same production line as it was the case with the 132s.

Shortround6 said:

Of course if one engine dies the whole plane is going to hit the ground in short order, that things was not going to stay in air on one 1000hp engine.

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Why not?

Well, that was one reason for using three engines in the first place.
So it would stay in air with 2/3rds power.
Trying to fly on 1/2 power with the controls fighting the airflow trying to trim the plane out (higher than normal drag).

Shortround6 said:

Well, that was one reason for using three engines in the first place.
So it would stay in air with 2/3rds power.
Trying to fly on 1/2 power with the controls fighting the airflow trying to trim the plane out (higher than normal drag).

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A host of other aircraft was able to land without calamity with just one 1000 HP engine operating.

A lot has to do with the power to weight or the surplus power available to actually fly.

A lot of planes could not stay in the air one one engine, just how far they got from the engine failure varied. Some planes had a negative climb rate on one engine. (Saro Lerwick, certain versions of the Whitley with lots of antennas, some Wellingtons were suspect.


A P-38 can fly on a lot less than 1000hp from one engine.
DC-3 can fly on one engine, early ones had only about 1000hp per engine or a bit less.
The Problem with the JU 52 is it needs a fair amount of power just to cruise at 130-150mph.

the DC-3 (in one version) could cruise at 205mph using 75% from both engines. Engines were rated at 1050hp at 7500ft max continuous so 75% was 75% of that, not take-off power.
Max speed (using 2550rpm/100% ) was 230mph. Stalling speed with flaps and gear down was 67mph. The DC-3 had a lot of room if an engine went out. This was at 25,500lbs (later ones got heavier)
The Ju 52 bludgeoned it's way through the air. It needed about the same amount of power to go 140mph (give or take) as the DC-3 did to go just under 210mph.
We know the cube root rule. The JU-52 and a number of other tri motors used the 2/3rds power to stay airborne.

Some planes were better than others. The Lerwick wouldn't even fly straight but descended in circles until it was reunited with the surface.
This is one reason for the canted engines on the Ju-52. It was supposed to make it easier to fly if the off side engine went out.

edit.
Info from the 1938 Jane's
Performance is a bit higher than Wiki, commercial plane, no gun mounts/turrets.
Top speed 180mph at 3,000ft.
Gross weight 23,200lbs
Climb to 1000 meters 4.8 minutes
Climb to 2000 meters 10.2 minutes
Climb to 3000 meters 17.5 minutes
Service ceiling 5,500 meters (19,020ft)
Ceiling with one engine stopped and weight of 20,900lbs......3,300 meters(10,824ft)

Shortround6 said:

The Problem with the JU 52 is it needs a fair amount of power just to cruise at 130-150mph.

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Take-off speed of the Ju 52 ( this is the heaviest condition) was supposed to be 120 km/h; landing speed of 106 km/h.
Stall speed of the much heavier DC-3 was 126 km/h.
(numbers are what I can fetch fast from Wikipedia)
Generous wing of the Ju 52 - 20% greater area than what DC-3 had - and lower weight seem to go a long way in providing a hefty amount of lift, and with it the low-speed abilities. So even if we won't go 270-280 km/h, there will not be exactly crashing down at 150-170 km/h either in an engine-out situation.

BTW - the propelleres as used on the Ju 52/3m were adjustable only on the ground, at least that was the case before 1940. So that's got to change with newer engines, too.

eta: Ju 52/3m, powered by 132A engines and with the props mentioned above, was supposed to gain altitude even with one engine out

from the 1938 Janes for the DC-3 with P & W R-1830 SCG

Speeds are a bit off.

max weight 24,800lbs
landing speed 67mph

initial rate of climb 1015fpm
Initial rate of climb with one engine (constant speed airscrews ) 185fpm
Initial rate of climb with one engine (feathering airscrews ) ...........235fpm
Service ceiling (two engines)....................................................... .............23,500ft
Absolute ceiling (two engines).................................................................25,400ft
Absolute ceiling one engine (constant speed airscrews)...............11,400ft
Absolute ceiling one engine (feathering airscrews).........................13,000ft


Remember that this is for a 15 degree C day at normal/standard air pressure.
The DC-3 is operating at 1/2 standard power, not 2/3rds.

Note that climb rate dropped to about 18-23% of normal depending on propellers,
Also note the ceiling dropped by around half.

Also note that the absolute ceiling is a bit of joke, I suspect calculated and not actual measurement. Service ceiling is climbing at 100ft per minute. with two engines it would have take over 20 minutes (well over) to climb from 23,500ft to 25,400ft.
Same for the single engine ceilings. If the plane is only climbing at 235fpm at sea level what is it doing at 9-10,000ft?

DC-3 with lower powered Wright Cyclone engines had an absolute ceiling of 7,500ft and when running 1700lbs light it was supposed to reach 9,500ft.
Again the likelyhood of reaching those altitudes or even maintaining them was pretty darn slim. It called for very careful flying, no banking and balancing on descending/stalling.
.

tomo pauk said:

BTW - the propelleres as used on the Ju 52/3m were adjustable only on the ground, at least that was the case before 1940. So that's got to change with newer engines, too.

eta: Ju 52/3m, powered by 132A engines and with the props mentioned above, was supposed to gain altitude even with one engine out

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The problem with the proposal is that while the Ju 52/3m would gain alitude on 2 engines it was going to do it slowly and it was doing it on 2/3rds (66%) power, not 50% power.

You also have the need to use more rudder and aileron deflection go straight as a twin than as a tri with one engine out (if it is the center engine you don't need much correction at all)

Low speed control also needs to be looked at The Blenheim had a ridiculously low stalling speed. But they wanted full rudder at less that 125mph, You also have to turn into the good engine. Turning into the bad engine can lead to problems trying to get out of the turn. The plane will want to skid outwards if adequate rudder pressure is not maintained to counter act the pull of the good engine and considerable opposite aileron may be needed to prevent over banking, it speed drops for any reason the spinning point be reached.
This is for the Blenheim other planes had different sized rudders and other different controls. Point is that if the plane will cruise faster on one engine you may need less rudder.
A two engine Ju-52 with one engine out may be skating close to the edge. You may have to fit a bigger vertical stabilizer and bigger rudder, not really that hard but this thing is marginal on power to begin with.

Shortround6 said:

The problem with the proposal is that while the Ju 52/3m would gain alitude on 2 engines it was going to do it slowly and it was doing it on 2/3rds (66%) power, not 50% power.

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You are of course right.
The Ju 86G was supposed to be able to fly at one engine at 7800 kg (BMW 132N) or at 7500 kg (132F), 170 km/h IAS. Ju 86G have had the landing speed of 120 km/h.
Obviously, the Ju 52 will need to dispose a good deal of fuel (a bit over 1800 kg was carried, max) in order to be still able to fly in horizontal with 900 HP instead of 1800.