Hawker Typhoon Question

[Pielstick]

From my reading over the years I've seen it often stated that the Hawker Typhoon was disappointing in its intended role as an interceptor because of its thick wing, which apparently limited its performance.

Then I've read that in 1942 the Typhoon was the only RAF fighter capable of intercepting the Fw190 raids coming across the Channel - the Spitfire MkV not being fast enough to catch the Fw190.

Is this not contradictory? I understand there were various other problems with the Typhoon yet the thick wing is often cited as its main drawback in the fighter/interceptor role... yet when it entered service it was the only 400mph capable fighter the RAF had?

[stever219]

The Typhoon's wing limited its high-altitude performance, but was not so detrimental at low level. The Fw190s were coming in on or near the deck to avoid the UK's radar chain and the fast, rugged Typhoon was at its best down there, as was proved when the War moved back into mainland Europe in summer 1944. The Tempest, with its aerodynamically thinner, more refined wing was better performer at all altitudes.

[Pielstick]

Surely the thick wing wouldn't be so much of a problem at higher altitude where the air is thinner? If anything the think wing would have been more of a hindrance at low altitude?

[JohnT]

Nick

Don't know the aerodynamics but Roland Beamont wrote about it in one of the books on my shelf. Read a while back but will dig out and let you know what he said

[Black Knight]

x

Edited January 26, 2014 by Black Knight

[Test Graham]

Put even more simply, the wing section was less important at altitude than the engine. The Sabre was not rated to give its best power output at the higher altitudes. Lots of power lower down, which helped overcome the drag of the thick wing. Not so good higher up.

The flow over the top of the wing does not create a vacuum. It only reduces the pressure. The lift comes from the difference in the flow between upper and lower wing surfaces - the air is thinner at high altitudes but that's as true for the top of the wing as the bottom. The angle of attack is increased by the pilot at high altitudes, but that's because the same angle gives less lift in thinner air, and lift has to equal weight. Eventually you do indeed run out of angle of attack, but that's as true for a thick wing as a thin wing. High altitude aircraft such as the Bristol 138 had thick wings. For any given angle of attack a thick wing will produce more lift than a thin wing and so will have better high altitude performance, if all other things remained the same. Which they never do, of course.

[Pielstick]

Graham I think you might be right about the engine having quite a lot to do with it. I think the Sabre only had a single stage supercharger?

Like I said, I had problems reconciling the popular reasoning that the Typhoon was a poor interceptor because of its performance limiting thick wing, yet at the same time it was faster than the Spitfire V at low altitude and the only RAF fighter capable of catching a Fw190 in 1942.

Be careful about attributing aerodynamic lift to Bernoulli.... Newton has got a say in it as well. Otherwise aeroplanes couldnt fly level upside down

[Test Graham]

Flying upside down just requires a greater angle of attack because you have a less efficient wing section - bear in mind that the position of the stagnation point is physically below the leading edge whichever way up you are flying. However, I am too long out of the lecture room to get involved in detailed arguments about the physics.

The engine is certainly the most dominant feature although wing loading helps too. Think of the variation between LF, F and HF Spitfires. Not just only a single-stage supercharger but the full throttle height of the design comes into it as well. What is often ignored is that a Spitfire LF Mk.V (ok, post 1942) also could and sometimes did catch an Fw190 at sea level: it was quite a "pocket rocket" but only up to 5000 ft.

[Pielstick]

Back in September when I was doing my Chief Engineer's ticket there was quite a heated discussion in the classroom about how torque is transmitted to the ship's propeller - is it via shear in the coupling bolts or is it via friction between the coupling faces in the transmission line?

Nobody could agree so the lecturer contacted a couple of companies that make power transmission components for ships and asked them. A design engineer at one company got in touch and explained that the torque transmission is around 85% shear, and 15% friction.

It reminded me a lot of the Bernoulli vs Newton arguments with aerodynamic lift - Bernoulli does the lion's share of the lifting, but he gets a little help from Newton

[wellsprop]

At high altitude the AoA needs to be increased. The increased AoA combined with the thick wing dirupts the air flow as it has to traver far further and rather than reducing in density it becomes turbulent and causes drag.

I think this is more or less why thick wings aren't good high up, I'll check my aerodynamics of flight book later

Ben

[gingerbob]

Going out on a limb here, but a thicker wing would tend to run into critical Mach sooner than a thin one. At higher altitudes the speed of sound tends to be lower (right?)- therefore there would be more of a limitation at higher altitudes- IF you could get there in the first place.

In addition to the performance dropoff at altitude (due to the engine, I mean), the Typhoon was also not as handy as the other fighters, which was seen as a drawback when considering it as a "general purpose fighter". Furthermore, it took a lot more maintenance than a Spitfire, so was not as "efficient" in that sense. Then of course there were the engine and airframe problems that persisted far too long.

bob

[Pielstick]

At high altitude the AoA needs to be increased. The increased AoA combined with the thick wing dirupts the air flow as it has to traver far further and rather than reducing in density it becomes turbulent and causes drag.

I think this is more or less why thick wings aren't good high up, I'll check my aerodynamics of flight book later

Ben

I think that the AoA would only need to be increased to achieve the same lift if the true airspeed remains the same? The same indicated airspeed would yield the same AoA if all other factors were the same. I may be wrong though?

Going out on a limb here, but a thicker wing would tend to run into critical Mach sooner than a thin one. At higher altitudes the speed of sound tends to be lower (right?)- therefore there would be more of a limitation at higher altitudes- IF you could get there in the first place.

In addition to the performance dropoff at altitude (due to the engine, I mean), the Typhoon was also not as handy as the other fighters, which was seen as a drawback when considering it as a "general purpose fighter". Furthermore, it took a lot more maintenance than a Spitfire, so was not as "efficient" in that sense. Then of course there were the engine and airframe problems that persisted far too long.

bob

Critical Mach, that sounds pretty plausible, and you're right this would be achieved sooner at higher altitude.

[Test Graham]

The speed of sound isn't that much slower at altitiude, although this was used by the early jet fighters in speed record attempts. The problem of reduced Mach limits is relevant to dive speeds rather than the normal flight envelope. It is common to read of aircraft (Typhoon, P-38, P-47, Spitfire) being unable to come out of a dive until lower altitudes are reached.

I agree that the AoA has to be increased at altitude to retain the TAS, but am unconvinced as yet that the flow over a thick section would necessarily break down earlier. There are two factors being talked about here - one is the lift curve slope, CL vs AoA, which will show the stall, and the other the induced drag curve CD against CL (usually CL squared). Induced drag is often considered to be reduced by high aspect ratio (as commonly employed on long range aircraft) but is not normally linked to thickness chord ratio.

Edited January 29, 2014 by Graham Boak

[wellsprop]

I'll upload a pic of my lift/AoA etc for a Pa28 as well as find my flight dynamics stuff

I should probably know this given I have an exam on it soon

The standard wing can be though of as the second aerofoil down. High lift but low speed (now good for hi alt) the thin wing is similat to he first aerofoil which works well at all altitudes due to the low drag http://www.allstar.fiu.edu/aero/images/fig18.gif

A thick wing just causes a huge amount of drag as AoA is increased when the air is less dense

Edited January 31, 2014 by wellsprop