P47 flight stability

[vfaco]

The DCS aircraft I've flown have less inertial stability than they should -- if the real F18 flew like the DCS version I would never have made it aboard the carrier in one piece. The P47, unfortunately, is the worst. It's a beautifully modeled aircraft but it flies almost like it's made of balsa wood. It's hard to look around the cockpit when it won't trim to hands off and stay where you put it. And it's almost impossible to fly formation. Tuning the flight control axis adjusts the sensitivity and range of the controls but does not affect stability.

 

Is there any way to increase the effective mass of the aircraft? Or am I imagining this?

 

Bob

[Art-J]

Apparently our P-47 has been modelled after 1953 NACA report TN 2899 (available on the net for free, I recommend taking a look), which revealed the real thing (D-30 at least, as that's the one that was flight-tested and described in the report) had a rather crappy longitudinal stability after all.

 

Makes the plane more difficult to fly than other DCS warbirds indeed, but it can be trimmed for hands-off allright, as long as the aux tank is empty and the speed is not low (the faster it flies, the more stable it gets).

[grafspee]

Actually modern planes are even worse, only thing which prevent modern jets crashing at every flight is advanced fly by wire systems which take most of the work from pilot.

P-47 have vey unusual weight balance, where substantial mass is located in tail section. Don't expect that this plane will be anything close to classics fighters.

With some practice you can do everything with this plane.

[grafspee]

Makes the plane more difficult to fly than other DCS warbirds indeed,

I don't agree with that, i would say that this plane needs different approach.

It it has some more complex stuff like engine management then others, yes.

With AUX tank full this plane indeed wants to kill pilot

[vfaco]

I agree, it can be trimmed hands off - that is, no stick force required. I guess my question is more about inertia than about stability. A body at rest tends to stay at rest, and neither the DCS P-47 nor the F-18 model that very well. It's sort of like balancing on top of a rubber ball. And I do agree about fly-by-wire. The F18, for example, was designed to be aerodynamically unstable for maneuverability, with inflight stability maintained electronically. But in the real world inertia is not a fly-by-wire function; it's just there. It has to be modeled into the sim.

 

The NASA report is interesting. Doesn't sound like they were very impressed with the machine. How soon they forget.

[SmirkingGerbil]

The DCS aircraft I've flown have less inertial stability than they should -- if the real F18 flew like the DCS version I would never have made it aboard the carrier in one piece. The P47, unfortunately, is the worst. It's a beautifully modeled aircraft but it flies almost like it's made of balsa wood. It's hard to look around the cockpit when it won't trim to hands off and stay where you put it. And it's almost impossible to fly formation. Tuning the flight control axis adjusts the sensitivity and range of the controls but does not affect stability.

 

Is there any way to increase the effective mass of the aircraft? Or am I imagining this?

 

Bob

 

Vfaco -

 

You fly the P-47 with the throttle, in essence the throttle is the Boost (Turbocharger)/Throttle and Prop Pitch controls. Locking the Boost lever to the Throttle, and Pitch full forward is the simplest way to explain it.

 

The R2800 generates a lot of torque, and will roll the airframe to the left with no trim to offset, it will also "walk the nose" of the aircraft if you change throttle positions suddenly, either by backing off of it, or firewalling (full forward) it. The torque will play havoc with hands-off flight.

 

With all things set, Throttle/Pitch/Boost all full forward, you can fly hands off trim by adding in Rudder offset towards "T.O." or Take Off trim, a smidge of Starboard trim bias (Right wing down), and with those settings you can trim out the P-47 and fly hands off straight and level all day. Just remember, any throttle setting, that changes engine power output or torque, will mean you will need to trim out the tendency of the engine to roll the aircraft to the left. Once done, she will fly straight as an arrow. Also, reducing power, reduces the torque, so if you are trimmed to fly straight and level at full power, reducing power will cause the aircraft to veer, just be ready to trim as needed.

 

Conversely, you can use throttle changes to modify flight trajectory, rolls, and even turns and gun runs to trim the nose in the direction you want. Comes in handy in a pinch during a dog fight.

 

That is how I fly her hands off - experts may disown this, I am just a noob, but this is how I fly the P-47 for hands-off, and it works quite well. Trimming for hands-off is second nature to me now.

[grafspee]

Is there any way to increase the effective mass of the aircraft? Or am I imagining this?

Bob

 

It does not matter to some extent. This is how i understand this.

CoG location is very important for the plane. In all warbirds CoG is before CoL then you need to induce some down force to prevent nose going down, so you need some down force to keep flying level.

When you pull stick in plane where CoG is quite forward before CoL then the mass of the plane is reducing effectives on the elevator.

But in case P-47 CoG is very close to CoL every input in elevator will feel like amplified.

In case where CoG will be behind CoL plane will be unflyable. Every even slightly pull on stick will induce self amplifying pitch up and stall or it would require larger air speed to be able to maintain level flight.

Because P-47 turbo installation is in tail section CoG is probably a lot closer then in other warbirds, this the reason why this plane feels very unstable.

 

[Pikey]

I have no idea what this thread is going on about. It flies hands off. And, very easily. It's super stable. Whats more, after I got my friend flying it, 5 minutes after take off I asked him, OK, trim it for hands off and see how stable it is. He told me he'd already trimmed it and was hands off.

 

He's an F-18 FBW guy.

[Nealius]

A body at rest tends to stay at rest, and neither the DCS P-47 nor the F-18 model that very well.

 

The only time a plane is at rest is when it's parked and the engines are shut off. In-flight, there is always wind, turbulence, and thermals acting upon the airframe. Even gliders are never at rest. In the case of warbirds, the spinning prop imparts forces on the airframe, like roll/yaw tendencies. Do some research on P-factor. Better yet, find your local glider club and ask for a 20-minute demo flight, and see for yourself.

 

Your claims on the Hornet and other flight modeling in DCS are completely unfounded. The modern jets like the Hornet (and Tomcat) are vouched for by former pilots of the real aircraft, who tell ED what needs to be fixed when something is wrong. Have you ever flown a Hornet? Or any plane, for that matter?

 

[grafspee]

I have no idea what this thread is going on about. It flies hands off. And, very easily. It's super stable. Whats more, after I got my friend flying it, 5 minutes after take off I asked him, OK, trim it for hands off and see how stable it is. He told me he'd already trimmed it and was hands off.

 

He's an F-18 FBW guy.

 

Thread is about why this plane has no mass, it should react to control inputs like a 747.

[SmirkingGerbil]

 

Thread is about why this plane has no mass, it should react to control inputs like a 747.

 

It doesn't??? I am with @Pikey on this one. She flies like a dream, but if you just jump in without trimming for torque etc. she is reactive to control inputs.

 

Just asking for clarification, to make sure I understand your statement.

 

Maybe my perception is based on the way I have set my curves, and I have all the flight/trim and engine management controls mapped to my A-10C TM Warthog HOTAS and Joystick - so my experience my not reflect others.

[kengou]

 

Thread is about why this plane has no mass, it should react to control inputs like a 747.

A nimble one-person prop fighter should control like a 747? Why on earth do you think that should be the case?

[Ironhand]

A nimble one-person prop fighter should control like a 747? Why on earth do you think that should be the case?

Hyperbole.

 

[Nealius]

No mass? Have you ever watched the nose during a roll reversal and felt how much rudder you need to keep this thing coordinated vs something like a Spit or Mustang?

[RodBorza]

 

Vfaco -

 

You fly the P-47 with the throttle, in essence the throttle is the Boost (Turbocharger)/Throttle and Prop Pitch controls. Locking the Boost lever to the Throttle, and Pitch full forward is the simplest way to explain it.

 

The R2800 generates a lot of torque, and will roll the airframe to the left with no trim to offset, it will also "walk the nose" of the aircraft if you change throttle positions suddenly, either by backing off of it, or firewalling (full forward) it. The torque will play havoc with hands-off flight.

 

With all things set, Throttle/Pitch/Boost all full forward, you can fly hands off trim by adding in Rudder offset towards "T.O." or Take Off trim, a smidge of Starboard trim bias (Right wing down), and with those settings you can trim out the P-47 and fly hands off straight and level all day. Just remember, any throttle setting, that changes engine power output or torque, will mean you will need to trim out the tendency of the engine to roll the aircraft to the left. Once done, she will fly straight as an arrow. Also, reducing power, reduces the torque, so if you are trimmed to fly straight and level at full power, reducing power will cause the aircraft to veer, just be ready to trim as needed.

 

Conversely, you can use throttle changes to modify flight trajectory, rolls, and even turns and gun runs to trim the nose in the direction you want. Comes in handy in a pinch during a dog fight.

 

That is how I fly her hands off - experts may disown this, I am just a noob, but this is how I fly the P-47 for hands-off, and it works quite well. Trimming for hands-off is second nature to me now.

 

I agree with all that. To add to it, I'd say that you fly the P-47 as you fly the Huey. Always compensating for torque and other forces. I use the rudder a LOT. But once you get it trimmed, you fly only with small inputs. However, if you move the throttle up or down violently, it will show. The nose will walk and it will get out of trim. It's not a simple bird to fly beacuse of the torque. But it gets easier once you pay attention to it.