Bf109 - why no bubble canopy ?

[tyrodtom]

I'm not saying the bubble canopy is a waste , but I think we might be overstating the need.
A good example of a single engine aircraft with outstanding rearward visibility is a IL-2, it had a rear gunner facing backward, with nothing to do but scan the sky to the rear.
But because a lot of IL-2 pilots were inexperienced, flew steady flights, trusting their rear gunner to see anything coming from the rear. Not thinking of the big area blanked out by the rear fuselage and tail.
The more experienced Luftwaffe pilots, seeing a IL-2 would just close the range in that blind spot, from below.

 

[vinnye]

That is what Hartmann said he did.
Maybe too much was made of the WW1 saying "Beware of the Hun in the Sun", maybe it should have been adapted to the catch phrase used in children's pantomimes - "He's behind you!"

 

[GregP]

When we have thought the bubble canopy was overrated, the next -generation conflict reminded us it wasn't.

We got the bubble canopy in WWII and kept it in Korea (SOON after WWII). Then we went to the first-generation supersonic planes like the MiG-21, F-8 Crusader, A-4, F-4, F-105, etc. Some LOOK like bubbles until you actually try to look out of the back and see the fuselage is rasied so you can't see behind you. The enemy in Viet Nam reminded us of it, and the next-gen (F-14, D-15. F-16) HAVE bubble canopies. So does the Raptor.

The Soviets had an entire generation without bubbles. Think MiG-25, MiG-27, Su-25, Su-24. etc. The new Russian fighters all have bubble canopies.

I don't think they were overrated at all. Giving the pilot the option to look behind him is imperative for survival. Whether or not he USES it is another question.

 

[Shortround6]

to be fair some of those 1950s jets were never intended to be dog fighters. Like the F-102 and F-106. They were intended to intercept bombers that had no escorting fighters. The F-105 has an "F" number but it was a bomber (primary role was nuclear attack platform, air to air was a secondary capability). No air to air fighter needed an internal bomb bay that could later house a 325 gallon fuel tank.

the "perceived" need (not actual) to hit mach 2 or close to it drove aerodynamics to override reward vision.

 

[GregP]

The "whys and wherefores" don't matter.

The simple fact is when we abandoned the bubble canopy, we were rudely reminded that we shouldn't have done that. There are NO top-line fighters without them today. So ... we must have learned that along the way, and SHOULD have learned it very well indeed in WWII.

 

[N4521U]

Besides the Germans probably thought the pilot looked like he was in a clear Joo Joo Bee.

 

[alejandro_]

I have been looking at diagrams of aircraft that received bubble canopy in latter version. None had a fuel tank behind pilot:

- Spitfire had main fuel tank in a section between cockpit and engine.
- Yakovlev aircraft had them in the wings.
- P-47s had them below pilot in the lower section of the aircraft (can someone confirm?).

If fuselage in Bf 109 is trimmed, you lose the fuel capacity and you have to lose range (which was already short) or relocate somewhere else (CG issues).

Another -more simple- reason pointed out in other forums was that Bf 109 was supposed to be phased out of production, thus it made no sense to develop time consuming improvements.

 

[Tante Ju]

If fuselage in Bf 109 is trimmed, you lose the fuel capacity and you have to lose range (which was already short) or relocate somewhere else (CG issues).

I don't think so, the fuel tank top ends somewhere at the lower canopy line, so if you trim down the real fuselage it would probably not effect the fuel tank much. And if it looses a bit in the top, you can always make it stretch a bit more towards the rear.

Besides after restoring the previous rear view with the fitting of the Galland Panzer, I do not think they would though that a further redesign and associated risk would be warranted. The Me 109 also had weak directional stability, perhaps this was a concern.

It would be interesting to know if this question was discussed at company meetings though, but lets not forget that - apart from Fw 190 - there were not many examples of bubble canopies until 1944. I am not sure when Typoon got one.

 

[paradoxguy]

I have been looking at diagrams of aircraft that received bubble canopy in latter version. None had a fuel tank behind pilot:

- Spitfire had main fuel tank in a section between cockpit and engine.
- Yakovlev aircraft had them in the wings.
- P-47s had them below pilot in the lower section of the aircraft (can someone confirm?).

If fuselage in Bf 109 is trimmed, you lose the fuel capacity and you have to lose range (which was already short) or relocate somewhere else (CG issues).

Another -more simple- reason pointed out in other forums was that Bf 109 was supposed to be phased out of production, thus it made no sense to develop time consuming improvements.

What about the North American P-51 Mustang? It did not have a bubble canopy fitted until the D-series, and I recall the B- and C-series (and later) had a large fuel tank behind the pilot's seat.

 

[stona]

I don't think so, the fuel tank top ends somewhere at the lower canopy line, so if you trim down the real fuselage it would probably not effect the fuel tank much. And if it looses a bit in the top, you can always make it stretch a bit more towards the rear.

This is exactly what I mean when I say people write "just" do this or that without really knowing what the ramifications might be.
I'm not picking on you Tante Ju It happens a lot in all sorts of threads.
I only caution against it because my research into various aircraft shows that modifications are never as simple to do as to write and are often extremely difficult. They often need months of development and testing before they appear in production aircraft. It's why places like Rechlin and Boscombe Down existed.
Cheers
Steve

 

[Tante Ju]

No problem at all stona, we are guessworking here. I guess so did the engineers in the 1930s - I wonder how many 'oops' were uttered by observing engineers when the test pilot was seen descending on a parachute... many times their calculations could not account for unseen problems like mach flutter, harmonic vibrations and so on..

 

[stona]

Absolutely correct. I've just been reading about problems with the elevator/elevator control circuit that led to the tail breaking off early Typhoons at the transport joint. It took several fatalities before finally the real cause was found. Oddly enough harmonic vibrations was one of the possibilities discussed, and eventually discounted In the meantime Hawker engineers kept going over their structural calculations and reporting that the structure was sound.

I appreciate you taking my post in the spirit in which it was intended!

Cheers

Steve

 

[Kryten]

Absolutely correct. I've just been reading about problems with the elevator/elevator control circuit that led to the tail breaking off early Typhoons at the transport joint. It took several fatalities before finally the real cause was found. Oddly enough harmonic vibrations was one of the possibilities discussed, and eventually discounted In the meantime Hawker engineers kept going over their structural calculations and reporting that the structure was sound.

I appreciate you taking my post in the spirit in which it was intended!

Cheers

Steve

I can shine a little light on this as I had a discussion with an old gent I knew who worked for Hawker and was part of the team trying to solve this!

He claimed the real problem was the elevators going into compression, you could move the elevators as much as you liked, once over the threshold they had no effect, the pilot then would throttle back trim out and pull like hell on the stick trying to recover from the dive, once the airspeed fell below the threshold the elevators suddenly regained authority and sent a huge load reversal through the fuselage breaking the transport joint!

It only happened in those circumstances, which was why they had such trouble finding the cause, he said they only really got to the bottom of it after the war when compressibility became understood!

Or that's the story I was told anyway!

 

[stona]

The official cause of the accidents was a failure of the elevator mass balance mounting brackets. The unbalanced control surface would flutter uncontrollably and impose unanticipated and enormous loads on the entire tail unit which then broke at the weakest point, the transport joint.
The cure was complicated. The following is from Mason.
1) The mass balance bracket was strengthened immediately as an interim measure that was retained.
2) Needle bearings were fitted in the elevator counter shaft. This enabled circuit tension to be increased without increasing control friction. Control backlash was virtually eliminated.
3)A correlation between the elevator mass balance moment and the tendency of the aircraft to tighten up in a turn was also established. A series of tests were flown with different elevator mass balance weights and varying inertia weights applied to the control column.
4) An 8lb elevator mass balance and a 16lb control column inertia weight were fitted.
5) The geared balance tab was changed to an ordinary adjustable trim tab and the damping cords were removed on the rudder.

Squadron Leader Beamont (NOT Beaumont!) then did diving trials up to 500 mph and pull outs in an effort, in his own words to "see if the tail would come off". They don't make them like that anymore. It didn't, luckily for him, and he also found that turns up to 61/2 g could be pulled at 5,000ft with no tendency to tighten up.
Strain gauges recorded that even in "harsh" pull outs at the highest attainable speeds no excessive loads were produced in the elevator mountings or transport joint.

Cheers

Steve

 

[Ivan1GFP]

I have been looking at diagrams of aircraft that received bubble canopy in latter version. None had a fuel tank behind pilot:

- Spitfire had main fuel tank in a section between cockpit and engine.
- Yakovlev aircraft had them in the wings.
- P-47s had them below pilot in the lower section of the aircraft (can someone confirm?).

If fuselage in Bf 109 is trimmed, you lose the fuel capacity and you have to lose range (which was already short) or relocate somewhere else (CG issues).

Another -more simple- reason pointed out in other forums was that Bf 109 was supposed to be phased out of production, thus it made no sense to develop time consuming improvements.

The later versions of the Spitfire Mk.IX and Mk.XVI actually gained fuel tanks behind the cockpit often along with a bubble canopy though in the Pilots Manual, it states NOT to fill that particular tank.

- Ivan.

 

[Ivan1GFP]

This thread has explored a lot of different ideas.

Way back in the beginning of the Me109 Improvements thread, I proposed that the tail be lowered to improve the ground angle. At the time, I was also thinking that it would help visibility a bit.

I have never seen a flying Me109 in person, but some of you probably have. Does the 109 fly a bit nose down like the FW 190? If so, then the tail would still block a lot of the view aft even if a bubble canopy were installed.

Here are a few other considerations:
The framing on the 109G and later was made thicker so that the cockpit could be pressurised even though most of the aircraft were not so equipped. The Germans were willing to lose even more visibility in ALL of their 109s with the heavier framing so that a few could received pressurised cockpits. A hinged canopy would also be simpler to seal than a sliding canopy.

With the original hinged canopy, no one is really inclined to taxi the aircraft with the canopy open. With a sliding canopy, perhaps this would be done. If this were done, with a heavy armoured canopy, perhaps the rails would need a fairly sturdy structure to be bolted to and this would be difficult with the design of the 109 aft fuselage.

Just a few different ideas.
- Ivan.

 

[stona]

Rear view was, and remained until the sliding one piece hood, a serious problem on the Typhoon. It was a major consideration for the RAF. Why the Luftwaffe was prepared to sacrifice this only it would know.
Cheers
Steve

 

[Tante Ju]

With the original hinged canopy, no one is really inclined to taxi the aircraft with the canopy open. With a sliding canopy, perhaps this would be done.

Or perhaps this was the reason why sliding wind panels were present on the hinged canopy? The Erla type of course, could not be opened this way, but also had only marginal framing.

 

[bobbysocks]

I don't think they were overrated at all. Giving the pilot the option to look behind him is imperative for survival. Whether or not he USES it is another question.

i agree and have never read a pilot complain or one state he didnt like a bubble canopy. even at that they installed a rearward radar on later 51s ( and probably other ac too ) to give advance warning if someone was closing in on you. my dad said there were a couple problems with it to his way of thinking. 1) like the mirror comment made by rall ...once the bell went off the EA was probably already too close. 2) it was turned off most of the time because guys were flying in formation and the bell would constantly be going off. in the heat of battle most pilots forgot to turn it on....hell a lot of them didnt remember to flip on their gun switches until they pulled the trigger and nothing happened. but the thinking i guess was if it saved a few pilots it was worth it. and that is the way i look at a better canopy on a 109....

 

[stona]

The Typhoon, canopy saga culminated in a report of actions by the Duxford wing on 19th August 1942. The Typhoons were bounced from above an behind three times, twice by Fw 190s and once by Canadian Spitfires.
There was a "clamour" for a better canopy. The current Stage B canopy incorporated flat windscreen quarterlights and did away with the small clear panels let into the structure behind the armour in favour of Perspex. The car door was retained. It was an improvement over the earlier type(s) but pilots reported that whilst straining to look over their shoulder and around the armoured head rest, vision through the rear Perspex at such an acute angle was so distorted that any aircraft within a 40 degree cone in the rear hemisphere was scarcely visible and impossible to identify, even if seen.
The new "tear drop" one piece sliding canopy was already being tested at Langley, but fitting it required such extensive alterations, including removing the car door, that it would be months before it appeared on production Typhoons and others were retro fitted.
It is important to note that the poor rearward vision from the early Typhoon canopies was considered a problem both by the pilots that flew it and the manufacturer who went to great lengths (and expense) to address the problem. It entailed major structural alterations at every stage of the progression towards the one piece sliding canopy of the late war versions.

Why the Luftwaffe appears to have had a different attitude I know not. I would imagine a pilot flying a Bf 109 after having flown a Fw 190 would at least comment on it, but it seems they just got on with it. Maybe they knew that the RLM would not authorise major surgery on the Bf 109 mid production.

Cheers
Steve