Some interesting facts to confirm about BF 109 Tail and Wing Radiators

[AX2]

Compared to the earlier Bf 109E, the Bf 109F was much improved aerodynamically. The engine cowling was redesigned to be smoother and more rounded. The enlarged propeller spinner, adapted from that of the new Messerschmitt Me 210, now blended smoothly into the new engine cowling.^[34] Underneath the cowling was a revised, more streamlined oil cooler radiator and fairing. A new ejector exhaust arrangement was incorporated, and on later aircraft a metal shield was fitted over the left hand banks to deflect exhaust fumes away from the supercharger air-intake. The supercharger air-intake was, from the F-1 -series onwards, a rounded, "elbow"-shaped design that protruded further out into the airstream. A new three-blade, light-alloy VDM propeller unit with a reduced diameter of 3 m (9 ft 8.5 in) was used. Propeller pitch was changed electrically, and was regulated by a constant-speed unit, though a manual override was still provided. Thanks to the improved aerodynamics, more fuel-efficient engines and the introduction of light-alloy drop tanks, the Bf 109F offered a much increased maximum range of 1,700 km (1,060 mi)^[35] compared to the Bf 109E's maximum range of ~1200 km (746 mi).

The canopy stayed essentially the same as that of the E-4 although the handbook for the 'F' stipulated that the forward, lower triangular panel to starboard was to be replaced by a metal panel with a port for firing signal flares. Many F-1s and F-2s kept this section glazed. A two-piece, all-metal armour plate head shield was added, as on the E-4, to the hinged portion of the canopy, although some lacked the curved top section. A bullet-resistant windscreen could be fitted as an option.^[36] The fuel tank was self-sealing, and around 1942 Bf 109Fs were retrofitted with additional armour made from layered light-alloy plate just aft of the pilot and fuel tank. The fuselage aft of the canopy remained essentially unchanged in its externals.

The tail section of the aircraft was redesigned as well. The rudder was slightly reduced in area and the symmetrical fin section changed to an airfoil shape, producing a sideways lift force that swung the tail slightly to the left. This helped increase the effectiveness of the rudder, and reduced the need for application of right rudder on takeoff to counteract torque effects from the engine and propeller. The conspicuous bracing struts were removed from the horizontaltailplanes which were relocated to slightly below and forward of their original positions. A semi-retractable tailwheel was fitted and the main undercarriage legs were raked forward by six degrees to improve the ground handling. An unexpected structural flaw of the wing and tail section was revealed when the first F-1s were rushed into service; some aircraft crashed or nearly crashed, with either the wing surface wrinkling or fracturing, or by the tail structure failing. In one such accident, the commander of JG 2 "Richthofen", Wilhelm Balthasar lost his life when he was attacked by a Spitfire during a test flight. While making an evasive manoeuvre, the wings broke away and Balthasar was killed when his aircraft hit the ground. Slightly thicker wing skins and reinforced spars dealt with the wing problems. Tests were also carried out to find out why the tails had failed, and it was found that at certain engine settings a high-frequency oscillation in the tailplane spar was overlapped by harmonic vibrations from the engine; the combined effect being enough to cause structural failure at the rear fuselage/fin attachment point. Initially two external stiffening plates were screwed onto the outer fuselage on each side, and later the entire structure was reinforced.^[33]

The entire wing was redesigned, the most obvious change being the new quasi-elliptical wingtips, and the slight reduction of the aerodynamic area to 16.05 m² (172.76 ft²). Other features of the redesigned wings included new leading edge slats, which were slightly shorter but had a slightly increased chord; and new rounded, removable wingtips which changed the planview of the wings and increased the span slightly over that of the E-series. Frise-type aileronsreplaced the plain ailerons of the previous models. The 2R₁ profile was used with a thickness-to-chord ratio of 14.2% at the root reducing to 11.35% at the last rib. As before, dihedral was 6.53°.^[34]

The wing radiators were shallower and set farther back on the wing. A new cooling system was introduced which was automatically regulated by a thermostat with interconnected variable position inlet and outlet flaps that would balance the lowest drag possible with the most efficient cooling. A new radiator, shallower but wider than that fitted to the E was developed. A boundary layer duct allowed continual airflow to pass through the airfoil above the radiator ducting and exit from the trailing edge of the upper split flap. The lower split flap was mechanically linked to the central "main" flap, while the upper split flap and forward bath lip position were regulated via a thermostatic valve which automatically positioned the flaps for maximum cooling effectiveness.^[37] In 1941 "cutoff" valves were introduced which allowed the pilot to shut down either wing radiator in the event of one being damaged; this allowed the remaining coolant to be preserved and the damaged aircraft returned to base. However, these valves were delivered to frontline units as kits, the number of which, for unknown reasons, was limited.^[38] These cutoff valves were later factory standard fitting for Bf 109G^[39] and K series.^[40][41]

 

Edited January 18, 2014 by Mustang

[JtD]

I hope this is only about the bold/red things, as far as I know:

 

The rudder was marginally reduced in size but retained airfoil and angle, see attached snippets.

 

A semi retractable tail wheel was indeed fitted.

 

The cut off options for the Bf 109F are documented in 1941 documents, but I don't know when they were introduced. They are also present in 109G and 109K documentation. The K-4 documentation mentions it was only used in the first few aircraft.

[Flyingpencil]

great job!

[Venturi]

 

In 1941 "cutoff" valves were introduced which allowed the pilot to shut down either wing radiator in the event of one being damaged; this allowed the remaining coolant to be preserved and the damaged aircraft returned to base. However, these valves were delivered to frontline units as kits, the number of which, for unknown reasons, was limited.^[38] These cutoff valves were later factory standard fitting for Bf 109G^[39] and K series.^[40][41]

 

 

 

 

ABSOLUTELY A MUST-INCLUDE ITEM

[Kurfurst]

Here is a picture lower cowling of the Bf 109G, showing the radiator cut-off valves installed (from a US report). For the 109F-4, these were much valued retrofits.

 

The operation was the following: there were one pull ring, roughly in the shape of that of a hand granade's safety pin ring, on each side of the lower-front of the cocpit, corresponding to the left and right radiator. When the radiator was damaged or leaking, the pilot pulled the ring on the appropriate side and it shut off coolant circuit of that radiator, and he could return to base on the remaining radiators coolant capacity. Very useful feature for any liquid engined fighter indeed!

 

A couple of interesting points - the 109G also introduced a light alloy, multi layer aluminum armored bulkhead behind the fuel tank. This a) protected the tank from small caliber hits from behind, and rendered incendiary ammo largely ineffective - though sadly, Russian HMG incidinaries seem to have still worked rather well. It also b) boosted the protection of the pilots steel armor, which, in that any bullet also had to pass through fuel tank, made the pilot pretty safe against any astern attacks from 7.62/12.7mm AP munition. This was also retrofitted to 109F series.

 

The 109F and G, K (probably the E, too for the cowl guns) also had an automatic, electro-pneumatic cocking and reloading mechanism for the 7.92mm, 13mm and 20 mm weapons, that automatically cleared the breach and reloaded (unjammed) the gun in case of a weapon jam upon releasing the trigger. The MK 108 equipped ones also had this option, but usually required interference from the pilot. I am not sure if the system worked for 20mm gondola guns - probably not though.

 

 

[RR1357]

Cut off valves for every aircraft wich had them.

[AX2]

Here is a picture lower cowling of the Bf 109G, showing the radiator cut-off valves installed (from a US report). For the 109F-4, these were much valued retrofits.

 

The operation was the following: there were one pull ring, roughly in the shape of that of a hand granade's safety pin ring, on each side of the lower-front of the cocpit, corresponding to the left and right radiator. When the radiator was damaged or leaking, the pilot pulled the ring on the appropriate side and it shut off coolant circuit of that radiator, and he could return to base on the remaining radiators coolant capacity. Very useful feature for any liquid engined fighter indeed!

 

A couple of interesting points - the 109G also introduced a light alloy, multi layer aluminum armored bulkhead behind the fuel tank. This a) protected the tank from small caliber hits from behind, and rendered incendiary ammo largely ineffective - though sadly, Russian HMG incidinaries seem to have still worked rather well. It also b) boosted the protection of the pilots steel armor, which, in that any bullet also had to pass through fuel tank, made the pilot pretty safe against any astern attacks from 7.62/12.7mm AP munition. This was also retrofitted to 109F series.

 

The 109F and G, K (probably the E, too for the cowl guns) also had an automatic, electro-pneumatic cocking and reloading mechanism for the 7.92mm, 13mm and 20 mm weapons, that automatically cleared the breach and reloaded (unjammed) the gun in case of a weapon jam upon releasing the trigger. The MK 108 equipped ones also had this option, but usually required interference from the pilot. I am not sure if the system worked for 20mm gondola guns - probably not though.

 

Kurfurst,  these data are very interesting. 

Thanks for sharing !

Edited March 1, 2014 by Mustang