Maneuverability vs Speed

[BarnOwlLover]

Maneuverability and Speed? Why not both? Though it does seem that a plane that's agile at higher speeds may not be able to achieve the same feats at lower speeds. And it does seem that planes that are good at low speeds often aren't as good at high speeds on the same coin.

It's sort of like comparing the Typhoon to the Tempest. The Typhoon had a thick, high lift wing, which stunted it's speed, especially at altitude (due to compressibility, though the single stage Sabre didn't help, either), but gave it good low speed characteristics for it's size (88mph landing speed was respectable for it's size and such), while the Tempest's wing was better for speed, though it did have a higher landing speed (about 100 mph, similar to most P-51s).

Also of note is how the Axis did things. Japan favored lightly loaded planes and low speed agility, Germany favored more heavily loaded designs optimized for speed and climb, while Italy designed (ultimately) speedy dogfighters. While the Allies ran the gamut, though they followed the bombers and favored high speed agility sort of like the Italians, though with often somewhat more lightly loaded designs that were easy to learn and fly (at least when airborne--the Spitfire wasn't at it's best in takeoff and landing when on the ground, though in the air it was a pilot's plane).

 

[GrauGeist]

And fearsome it was.

"The Messerschmitt Me 262's most dangerous opponent was the British Hawker Tempest - extremely fast at low altitudes, highly-manoeuvrable and heavily-armed."

(Hubert Lange, Me262 pilot)

"At low altitudes..."

The Me262A-1a, the most common type in service, rarely engaged in combat at low altitudes.

However, they did have to take-off and land (aka Rat Scramble) in a hostile environment. This was their Achilles' Heel.

 

[GregP]

In truth they were all after it all. faster, better rate of roll, turn and climb. The Zero was agile because it was light, it was light to give it a huge range. The Spitfire had a good rate of turn because it had a good rate of climb. All sorts of things were done to the Spitfire improve rate of roll throughout its service ending up with completely different wings. Same for the P-51 and especially the P-38 with powered ailerons etc.

Rate of climb is related to power-to-weight, not turn rate. Turn rate is related to wing loading, which is directly tied to weight and wing area.

 

[drgondog]

Rate of climb is related to power-to-weight, not turn rate. Turn rate is related to wing loading, which is directly tied to weight and wing area.

Strictly speaking ROC is related to delta Power Available less Power Required (Drag mostly) and Weight. Also rate of turn is function of( G* CL and inverse of W/S)^2

 

[pbehn]

Strictly speaking ROC is related to delta Power Available less Power Required (Drag mostly) and Weight. Also rate of turn is function of( G* CL and inverse of W/S)^2

I was referring to sustained turn and climb. As I understand it at any given altitude sustained turn and climb are very similar, generating a turning force not a climbing force. There must also be a value for "instantaneous climb" as there is for instantaneous turn, but it has little use in most discussions. Or have I got it wrong?

 

[drgondog]

I was referring to sustained turn and climb. As I understand it at any given altitude sustained turn and climb are very similar, generating a turning force not a climbing force. There must also be a value for "instantaneous climb" as there is for instantaneous turn, but it has little use in most discussions. Or have I got it wrong?

The instantaneous turn limit acceleration and velocity is at the max G and CLmax limit, past which one stalls or dies in the structural failure.

The equations for turn are very similar to a loop with obvious constraints on how to address weight as an accelerator/decelerator factor

 

[GregP]

Strictly speaking ROC is related to delta Power Available less Power Required (Drag mostly) and Weight. Also rate of turn is function of( G* CL and inverse of W/S)^2

Technically, as always, you are correct. That would be power available over and above power required for level flight. I think I covered W and S, and I made an assumption that a top fighter would have a very good CL Max. The planes without a good CL Max somehow don't usually make the grade as top fighters. I could be wrong, but the top fighters seem to have similar CL Maxs.

Also, most all turn calculations are calculated as a level turn since it is assumed that the max turn at low level would necessarily not entail much altitude loss without contacting terra firma. The level-turn calculations go out the window if you climb or descend much while in the turn. I buy sustained turn rate as similar to a climb in capability, but the angle of attack is different. I assume more angle of attack in a hard turn than in a steep climb. You'll likely stall out of a hard, near-limit turn before a near-limit steep climb, if only due to more practice at max angle climbing than in hard turning.

At least, when I fly, I generally climb at either Vy or Vx, depending on the field length and surrounding obstacles. It's usually much more critical in an off-airport Alaska scenario than in the midwest, where tall trees aren't usually rooted at the end of the runway that is always longer then you really need, but I usually practice one or the other every time I fly. Not so with a hard, near-the-limit turn. My worst turns are usually steep turns at maybe 60° bank angle, not 90° combat turns trying to shake someone who is trying to kill me. I've only done 90°+ banks in an aerobatic plane a few times. I think fighter pilots tend to practice hard turns way more than that, but I bet they still practice Vy or Vx climbs more often than they do hard, near-limit turns.

Could be wrong.

 

[SaparotRob]

I love that kind of talk.

 

[drgondog]

Technically, as always, you are correct. That would be power available over and above power required for level flight. I think I covered W and S, and I made an assumption that a top fighter would have a very good CL Max. The planes without a good CL Max somehow don't usually make the grade as top fighters. I could be wrong, but the top fighters seem to have similar CL Maxs.

Also, most all turn calculations are calculated as a level turn since it is assumed that the max turn at low level would necessarily not entail much altitude loss without contacting terra firma. The level-turn calculations go out the window if you climb or descend much while in the turn. I buy sustained turn rate as similar to a climb in capability, but the angle of attack is different. I assume more angle of attack in a hard turn than in a steep climb. You'll likely stall out of a hard, near-limit turn before a near-limit steep climb, if only due to more practice at max angle climbing than in hard turning.

At least, when I fly, I generally climb at either Vy or Vx, depending on the field length and surrounding obstacles. It's usually much more critical in an off-airport Alaska scenario than in the midwest, where tall trees aren't usually rooted at the end of the runway that is always longer then you really need, but I usually practice one or the other every time I fly. Not so with a hard, near-the-limit turn. My worst turns are usually steep turns at maybe 60° bank angle, not 90° combat turns trying to shake someone who is trying to kill me. I've only done 90°+ banks in an aerobatic plane a few times. I think fighter pilots tend to practice hard turns way more than that, but I bet they still practice Vy or Vx climbs more often than they do hard, near-limit turns.

Could be wrong.

No, Greg - not wrong. And clarity about ability to turn at a 'performance calc' rate is assumed max for level altitude constant turn. Excess power plays there also.

The P-51 NAA/NACA 45-100 CLmax was a bit lower than comparable NACA 230xx (P-38, Bf 109, F6F, F4U, FW 190) and the Spit wing. That said, the 45-100 drag was quite a bit lower in zero lift (cruise and high speed specifically). A P-51 in turning fight with a 109 in the medium speed range - equal skill assumed - should carefully consider his options. With a Spit he should not be there at all.

Only the best pilots could navigate At (or very close) to wind tunnel CLmax in their fighter without stalling out so the advantage at high AoA was not so much.

At the end of the day, Perfomance Calcs, based on sound mathematics describing the physics of a perfectly built airframe in smooth air as boundary conditions - are only an engineering sandbox to play in. One of the advantages of an aero education is that part of the curricala encompasses why the real world offers many surprises to the elegance of theory.

 

[GregP]

Eloquently put, Bill.

I like that ... "surprises to the elegance of theory."

By the way, I got to take a ride in the EAA's Ford Trimotor last Thursday. It surprised me. Accelerated nicely, short take-off, good climb. Relatively quiet cruising. Short landing. I see why people liked them. Got me to wondering about it and I found this:


View: https://youtu.be/GZ2hO9QS5ow

In my ride, I didn't fly with this guy! Not too sure I would have wanted to, even if offered the chance.

 

[special ed]

I'd like to see him try that with a Ju 52.

 

[GregP]

Me, too.

 

[SaparotRob]

Eloquently put, Bill.

I like that ... "surprises to the elegance of theory."

By the way, I got to take a ride in the EAA's Ford Trimotor last Thursday. It surprised me. Accelerated nicely, short take-off, good climb. Relatively quiet cruising. Short landing. I see why people liked them. Got me to wondering about it and I found this:


View: https://youtu.be/GZ2hO9QS5ow

In my ride, I didn't fly with this guy! Not too sure I would have wanted to, even if offered the chance.

Amazing.

 

[GrauGeist]

Eloquently put, Bill.

I like that ... "surprises to the elegance of theory."

By the way, I got to take a ride in the EAA's Ford Trimotor last Thursday. It surprised me. Accelerated nicely, short take-off, good climb. Relatively quiet cruising. Short landing. I see why people liked them. Got me to wondering about it and I found this:


View: https://youtu.be/GZ2hO9QS5ow

In my ride, I didn't fly with this guy! Not too sure I would have wanted to, even if offered the chance.

I rode in EAA's Trimotor several years ago.

Of all the aircraft I have ever ridden aboard, the Trimotor was the smoothest, most comfortable ride I have ever experienced.

 

[GregP]

I had that feeling, too, GrauGeist. Seemed like a really nice airplane to fly and seemed to do everything well.

My overriding impression was that it was a solid, good-flying airplane. Now I understand why Bushmaster made two new-build units. Kind of surprised it didn't "make it," because all you need to do to like it is go for a ride in it. I assume that flying one would be a great thing to experience. I talked at some length with the EAA pilot and he has nothing but good things to say about it. Keep in mind we were flying from the Planes of Fame, where there are a LOT of flying old airplanes.

 

[GrauGeist]

I'll be 100% honest when I say that the interior, seating and ride reminded me of riding in a School bus when I was a kid.

Sensory overload of nostalgia going on right there!

By the way, I posted a thread about the EAA's Trimotor visit to Redding (RDD) here (complete with pix):

EAA Ford Trimotor visits Redding Airport (RDD)

Last week, we had a vist by the EAA's Ford Trimotor here in town (Redding Municipal Airport) and it was great to see vintage aviation up close and personal! I went down on Friday (29 May) afternoon and took some photos and we had a suprise visit by a Gentleman and his Wife in their 1932 Ford...

ww2aircraft.net