A question about flying qualities

Ojisan_alpha

Hi guys,

I'm certainly not the first one to express my deepest admiration for that amazing Vulcan!

However, I have the impression that the handling at low speeds could be improved a little.
Background info:
I'm trying to replicate XH558's flying display.

Points I noticed:

It feels as if pitch authority (or, rather, pitch up totation rate) is lacking in certain areas of the flight envelope.
I wasn't able to recreate the quick nose-up pitch on top of the wingover.

For comparison:
https://youtu.be/X98ZnZs-2ds?si=9uxPOoD4HS2PjVMs&t=58
Even full-up elevator cannot produce the result one can see in the video above.

The same happens when I try to recreate the roll from a loop that is described by Tony Blackman: Pitch up with 3g from 280 kts (at 20% fuel load), and she can hold those 3g until about vertical (at SBAC the prototypes were certified for 3g) - but then the elevator authority rapidly vanishes and she's hardly able to pull 0.75g, resulting in a far too low airspeed on top of the looping (it ought to be 150 kts).

To me it feels as if the elevator authority falls off too quickly below 200 kts.

She's lacking power
The combination of a tight turn and steep climb immediately after takeoff cannot be recreated:
https://www.youtube.com/watch?v=OhHe79Yge2U

558 had a thrust to weight ratio of about 0.7, therefore she was able to keep a 45 degrees climb without speed loss - but I wasn't able to reproduce those numbers, even with only 20% fuel.

I've been trying to recreate Kev and Bill's famous last pass of RIAT 2015, but starting from 300 kts I'm unable to climb to more than 5000 ft before running out of speed - in this pass 558 climbd to 7.500 ft and still had enough speed for a controlled wingover.

Trying to keep the speed between the 160 and 180 kts used by 558 is quite hard - pitching up just a little too steep and she'll run out of speed extremely quick (much faster than I'd expect her to from what I've seen from the real 558).

Additionally, wingovers are problemativ because the real ones often ended up in a 20-25 deg nose down attitude, yet 558 always easily pulled out of this attitude without the need to use airbrakes.
In JF's 558, pulling out of this attitude is very, very problematic due to the lacking elevator authority, even if you manage to keep the speed below 200 kts.

Adverse yaw
I feel as if adverse yaw could be more pronounced - I don't need any rudder at all.

If necessary I could go deeper into details if it can be of any help to you guys.

I know I'm talkingh about a strategic bomber that shouldn't fly aerobatics, but I'd be rally grateful if you could look into that. Otherwise she's pretty perfect.

Cheers
Andreas

reference:
https://vintageaviationecho.com/vulcan-xh558/

p.s.
Did I mentioin that I absolutely love the stall modelling?

Delta558

is under discussion, I'm waiting for further feedback from Vulcan pilots. The ratio of effectiveness is correct (the drop off from low speed to high speed), that was worked out from diagrams and graphs in the servicing manual. It's possible it may need a 'bump up' of the basic effect
Not lacking power. The power is correct for both engine types. I presume for this you are using the 558 VTTS livery, which has its own flight model? I tend to use the 'normal' flight model and the 200 series engines because I grew up watching Vulcan displays in the 80s and 90s - generall flown at 130,000lb AUW. With that setup I can clear 5000ft comfortably on that RIAT-style wingover, so I would expect the VTTS one to manage it but I'm not sure of their AUW for that display.

Your paragraph about "pitching up a little too steep and she'll run out of speed" I can best counter with a quote from Dave Thomas (VDF, early days of VTTS). Unfortunately I'm paraphrasing because I am in work without access to the text at the moment but he describes the 90s displays as "like flying a big flat plate through the air. That's why the displays were so noisy, we sat there at low speed balancing power against drag. If the speed started to drop, there was so much power you just unload the wing for a few seconds for the speed to recover and then heave back into the drag."

I've been having a bit of fun with the wingovers myself - it's noticeable that the wings aren't held vertical for any length of time, once the nose starts dropping there's a quick roll off of the bank but that transition (for me at least) is not as straightforward in MSFS as we had it in P3D and X-Plane. Noticeable, though, is that in the 90s the airbrakes often were used on the way out of the wingover.

There will be minor adjustments at some point to the above. Tweaks, based on direct feedback from Bill Ramsey. We'll see where we get to.

adverse yaw - I wanted more, far more. I have discussed this with Bill and Mike Pollitt, their reaction was all I needed to know and confirms the video evidence. Did you know that wingovers in the low-speed regime could be accomplished entirely on rudder? Often, it was better to lead with rudder to achieve a coordinated turn.
I have set the aileron drag levels excessively high and yet MSFS does not want to know. I will keep working away at that one because it is one of the areas of the flight model I am least happy with.

I will also add that trying to recreate the behaviours of a big Delta wing in MSFS is not the easiest - both P3D and X-Plane allowed enough adjustment to nudge things in the right direction. MSFS just does not allow that, the core flight model dictates far too much but I am hopeful that with more control given back to us in the next version of this game I will be able to build on this base and create something which is really tuned-in!

Ojisan_alpha

Hi Delta,

cool username. :)

Concerning the running out of speed:
I have the feeling that energy bleed at high AoAs is good, but tried unloading her in steep climbs (zero G, to keep (induced) drag as low as possible), and this didn't help unfortunately - she's still not climbing as high as I'd like her to. Give me a little time and I'll do some precise comparison flights with the real 558's videos.
I'm flying 558 with 25 percent fuel, resulting in an AUW of about 103.000 lbs.

On the other hand: Nit picking here. ;)

I'm not sure about the adverse yaw though. Knowing how much rudder coordination the real Vulcan needed and how badly she behaved in a sideslip I think a significant number of customers would be overwhelmed.

Cheers!

Delta558

@Ojisan_alpha Okay, it has been a few weeks but I have feedback:

Bill Ramsey has flown the MSFS version, albeit briefly, and has made a couple of comments which may require looking at BUT he said that, if anything, it was slightly too pitchy!!

I really didn’t have any issue with the flight characteristics. Maybe slightly pitchy but honestly I’m not used to the stick so quite probably that was what I was seeing.

Bill uses X-Plane mainly, and has his own YouTube site with plenty of videos including our X-Plane Vulcan (well worth a visit). He doesn't currently use MSFS on his own computer, but has access and I'm hopeful that he may give some more feedback as and when he gets a chance to play a bit more! As well as all this, Bill is very involved with https://www.peoplesmosquito.org.uk/ - a very worthwhile cause and I hope to see a decent version of that in MSFS someday soon!

Ojisan_alpha

Thx a lot for your insight.

The more experience I get with XH558 the better the flight model feels. At the moment my only serious problem is the lack of pitch-up rate on top of a wingover at 140 kts - hardly any elevator authority there, and still unable to replicate this:
https://youtu.be/B092qvttZGU?si=pLZ_Mu7FGps8UUMG&t=347

However... nitpicking on high niveau - I increased elevator deflection one degree which suits me better. ;

Well.... the mosquito would be an extremely nice addition. :)
With a lot of luck my name might be in the bomb bay door - as it is on XH558.

Long time ago I spent an hour with Kev at RIAT talking about the Canberra... such a pity that it itn't succeed (yet)... and times don't get better for such a kind of enterprise....