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razbam av8b harrier revisited

K

kdfw

Charter Member
got the harrier recently, about couple of years after the initial release.

i was rather worried about what i read about the vtol aspect of the flight dynamics, and unfortunately, couldn't find a single video that showed the vertical to ff and ff to vertical transitions.

now that i have the model, i could now see what the issues were and my quick impressions on this aircraft:

1. vc and external models are outstanding.
2. fwd flight behavior is fine.
3. vtol module exhibits nonlinear behavior, could've been refined:
a. ff to vtol transition at 99 kts, any stick input gets amplified, becomes 'uncommanded nose up.' if stick is neutral, it's fine--trim elevator up so stick can be released at 100kts. fde should've masked the stick input at the transition point and gradually ramp to the stick reading to fix this.
b. hovering at slows speeds, throttle response is very slow, tends to lead to porpoising, or sometimes just cause the harrier to fall out of the hover. extremely annoying.
c. at slow hover < 10kts, sometimes forward speed suddenly hits zero and turns into an elevator of sorts. can't always replicate this, very annoying.
d. thrust varies with nozzle angle so constant compensation is needed to control.

but all in all, it's an excellent product. video below shows vertical to ff to vertical landing. bounced at landing but one of the best one i made so far.

and yes, fsx doesn't provide a good framework for v/stol models, but if you're familiar with Fred Naar's HTR fde for helicopters, same type of thing could've been done for v/stol aircraft.


 
Great film, but how do you avoid the aircraft's nose lifting violently upward when landing as you pass through 100 knots? I've always had this problem and to me it spoils an otherwise great model.
I know the Harrier was a difficult aircraft to fly, and the RAF only chose their best pilots to train for it, but if it was rally like the RAZBAM's flight dynamics you would be losing pilots every day.


Ian
 
In the last week, I too took a flight in this aircraft after having it sit in my hangar for a long time.

I shared your exact experiences. Very frustrating as even with the nozzles full aft in CTOL, the jet would still revert to STOL. I also had trouble with the autopilot capturing an altitude and following waypoints. I'll read more into that, as I believe that was my doing.

Jeff
 
Yes, it's a shame that RAZBAM couldn't have ironed out some of these issues. There are some very nice details in their Harrier and I know they put a lot of effort into it.

The pitch up can be mostly avoided by making sure that the aircraft is in trim as it's an increased sensitivity issue to account for the reduction in aerodynamic control effectiveness that's the culprit here. It's annoying, but it is a slap on the wrist for not trimming your aircraft that's for sure! ;)

Storm, if it helps, the actual AV-8B has neither auto altitude capture nor Nav mode. The AP modes are limited to Attitude Hold, Altitude Hold (manually engaged) and sort of a pseudo Heading Hold (manually selected...no heading select available).

If you are willing to give up some of the eye candy, SSW's incorrectly named "Lawn Dart" version of the AV-8B actually has a very nice VSTOL model with not only a correctly working VSTOL performance page in the MPCD, but also pretty realistic behavior when you don't heed it! :D

Deacon
 
Deacon211 said:
Yes, it's a shame that RAZBAM couldn't have ironed out some of these issues. There are some very nice details in their Harrier and I know they put a lot of effort into it.

The pitch up can be mostly avoided by making sure that the aircraft is in trim as it's an increased sensitivity issue to account for the reduction in aerodynamic control effectiveness that's the culprit here. It's annoying, but it is a slap on the wrist for not trimming your aircraft that's for sure! ;)

Storm, if it helps, the actual AV-8B has neither auto altitude capture nor Nav mode. The AP modes are limited to Attitude Hold, Altitude Hold (manually engaged) and sort of a pseudo Heading Hold (manually selected...no heading select available).

If you are willing to give up some of the eye candy, SSW's incorrectly named "Lawn Dart" version of the AV-8B actually has a very nice VSTOL model with not only a correctly working VSTOL performance page in the MPCD, but also pretty realistic behavior when you don't heed it! :D

Deacon
Click to expand...

Deacon is right, if you want a realistic FDE for this aircraft, then I suggest you to have a look for the SSW model, which is one of my top three aircrafts in my FSX hangar!
 
Very clean transitions, well done! Even Razbam's own video didn't hold a candle to that.

That was my chief annoyance with that aircraft; its transition behavior. I was so annoyed with the clunkiness that I gave it full time residence in my boneyard. After your video, maybe I'll do some more tinkering.
 
Funny, how some will say the SSW Harrier is more realistic? It's easier to handle in VTOL mode, thanks to Robs fantastic VTOL module. And everyone can have a taste of that module when using Dino's F-35B.
But to call it realistic goes a bit beyond rediculous. If they had incorperated Robs VTOL module in the real Harriers, the RAF would have never had to choose the best pilots available, ever!
I'm not saying the Razbam FDE is more realistic, I'm not, in fact none actually is, but to create a close to real hard workload during VTOL operations, than the Razbam Harrier certainly can give one that thrill.
And besides practise makes perfect.
Compare it to people who like a more realistic start up....to people who just like to use CTR-E only, heavy workload......no workload. :adoration:

But everyone can choose their own preferences, as this flightsim.

Kdfw. thanks for sharing your vid, it was a pleasure to watch. Maybe it should be put on Razbam main site?


Cheers,
Hank
 
hae5904 said:
I'm not saying the Razbam FDE is more realistic, I'm not, in fact none actually is, but to create a close to real hard workload during VTOL operations, than the Razbam Harrier certainly can give one that thrill.
Click to expand...
Don't get me wrong, I actually like the Razbam Harrier. But the FDE below 100kts defies simple physics. I've never flown a Harrier, but I would assume that the difficulty in VTOL operations does not come from sudden stops from 10kts to 0kts, or from losing all inertia below 100kts. Apart from that, the Razbam Harrier is actually extremely stable and easy to fly while hovering, for example you can bank it to 60° and barely go sideways, again something that is probably not possible in the real one. Frankly, after one or two flights with it I've lost all interest to practice VTOL.

On the other hand, STOL is possible and from what I've heard more common anyway, the model and the VC in particular are beautiful, sounds are nice, and it's just really fun to fly! :)
 
as mentioned here, 'uncommanded nose up at 99kts' issue can be mitigated by forcing the stick to the neutral elevator position at 100kts ias. to prevent the nose from falling at that time, trim up before hand. i set up trim 20 clicks around 120kts to get ready for the 99kt vtol transition point. awkward mode transition but it works.

one thing i noticed is that vtol mode kicks whenever speed falls below 100kts, so can't stall the thing in normal flight....

@hae5904
razbam is welcome to use the video. i was going to record more landing sequences to understand what exactly causes the model to suddenly sink so maybe i can put together a tutorial of sorts.
 
I agree there is a major difference between these STOVL FDE Modeling's versus a real Harrier. I have heard it directly from the horse's mouth (MCAS Cherry Point Harrier Pilots) who say getting the Harrier into and maintaining a hover is like trying to balance the jet on a needle point. The F-35B on the other hand is noted as being super stable and easy to transition and land due to it's FBW system and a surplus of thrust from the engine nozzle and lift fan. Still, in FSX, vertical flight is not at all a perfect science, at best a rudimentary attempt at it.
 
Just to clarify some things:

- It is true...SSW Harrier use "one" RobBarendregt Vstol module, not the well known RB VStol Module (it is not the same of the Wilco or the old Iris models or others models which use it). We have made some work toghether with our friend Rob for the new module and we have created a new dll to improve, and get a more relistic behavior in VStol operation (SideSlips, GroundEffect etc...)

- Our FDE in VStol Operation and normal flight was flown by at least 2 Harrier Former Pilots, one from the Italian Navy (The first Italian Former pilot and Instructor of Harrier) , and one from the USMC. They give us very interesting feedback about all the operation, and the behaviour of the aircraft in different configurations. They were very satisfied about the results of fde model.

Every models have merits and defects, eachone can choose the model which is nearer what he is looking for....

Regards
Emanuele
 
hae5904 said:
Funny, how some will say the SSW Harrier is more realistic? It's easier to handle in VTOL mode, thanks to Robs fantastic VTOL module. And everyone can have a taste of that module when using Dino's F-35B.
But to call it realistic goes a bit beyond rediculous. If they had incorperated Robs VTOL module in the real Harriers, the RAF would have never had to choose the best pilots available, ever!
I'm not saying the Razbam FDE is more realistic, I'm not, in fact none actually is, but to create a close to real hard workload during VTOL operations, than the Razbam Harrier certainly can give one that thrill.
And besides practise makes perfect.
Compare it to people who like a more realistic start up....to people who just like to use CTR-E only, heavy workload......no workload. :adoration:

But everyone can choose their own preferences, as this flightsim.

Kdfw. thanks for sharing your vid, it was a pleasure to watch. Maybe it should be put on Razbam main site?


Cheers,
Hank
Click to expand...


Well Hank, I'm sorry but I'm going to have to stop you right there.

I really really try to stay out of the "Great Harrier Wars" as I have and fly both the RAZBAM version and the SSW version and enjoy them both. But I have flown the Harrier and I think you are making statements that are a bit disingenuous here.

RAZBAM's version is beautifully modeled and sitting in the cockpit just feels more like the real thing with a great and mostly realistic HUD (There are many small to middling issues with the symbology, but they will generally be unnoticeable to most people). They have a very cool FLIR presentation, a wider selection of ordnance than SSW's bird, a much easier configuration interface (with a VSTOL fuel easy selection) and significantly, the RAZBAM bird can fly a FSX loaded flight plan without the extra file editing that SSW requires.

But the SSW Harrier simply has the better flight model. Not perfect mind you. The SSW engine has substantially more thrust than even the best Harrier engine. But largely the effect of this is simply to allow you to perform VSTOL at a greater range of weights than you would be able to do in real life. That's a good thing as I have never quite been able to light load the jet for VSTOL via the interface which is a benefit of the RAZBAM menu.

The SSW VSTOL module is also somewhat more forgiving than the jet in regards to the "edges" of the flight envelope. It is not as critical as the jet in zeroing your sideslip. It benefits (as I've stated) from generally having a little more excess thrust than the real airplane and it's a good bit less twitchy. Think of it as a Harrier envelope with bumpers.

For all that however, the SSW Harrier has very believable transitions, fully controlled throughout. The decel to a hover (and accel from one) both have the ability to give me a little Déjà Vu. The short take off works as advertised and, when I was getting a little too FSX-ey by the way of not checking my VREST page for adequate landing performance, the SSW Harrier did subtly run me out of power as I slowed for an RVL dropping me out of the sky with insufficient thrust to either land or accelerate back onto the wing. That's a pretty believable flight model.

The RAZBAM Harrier simply has all the issues that KDFW noted above in VSTOL. I spoke with RAZBAM (unfortunately just too late to make a difference) about the FM and I can tell you that they were working their behinds off to iron out these issues. But they ran into the "fix one thing, break another" cycle that I can't appreciate but FM gurus here I'm sure can. I by no means look down on those guys for the issues they ran into taking a Cessna flight model and trying to "McGuyver" it into a transonic VSTOL jet one.

Now, as I have said, I generally try to avoid taking sides in this contest between two design houses both of whose work I respect. Were I king for the day, I would combine the best attributes of RAZBAM's Harrier with those of SSW's to produce the best Harrier sim ever made.

But, when I hear the sentiment (generally stated disparagingly) that more difficult is by definition more realistic, I feel it necessary to point out how overwhelmingly untrue that generally is. Flying aircraft can be difficult. Flying sims can be difficult, perhaps for the same reasons, perhaps for different reasons entirely. But simply substituting difficulties and declaring it more realistic is a wholly illogical argument.

Again I apologize for jumping in here, but I feel something was being said that wasn't quite accurate. No offense is intended to either company as I personally couldn't design a brick and make it fall within the FSX environment.
 
Deacon211, don't get me wrong as I only made a general statement about someone mentioning the statement of "realistic" . And as you could have read, NONE is realistic.
So post is not even close about a contest!
I only mentioned about the highter cockpit workload during a VTOL landing, and as you said you'd flown Harriers before, you actually should know that.

And again, nothing about lighten up a fire (again....way behind us).

Cheers,
Hank
 
hae5904 said:
Deacon211, don't get me wrong as I only made a general statement about someone mentioning the statement of "realistic" . And as you could have read, NONE is realistic.
So post is not even close about a contest!
I only mentioned about the highter cockpit workload during a VTOL landing, and as you said you'd flown Harriers before, you actually should know that.

And again, nothing about lighten up a fire (again....way behind us).

Cheers,
Hank
Click to expand...

Hank, I just said that the FDE of the SSW model is a "realistic" one, and this is declared not only by me, and we all know that "realistic" in the FS world doesn't means that perfectly fit the real counterpart.
I don't want to make comparisons since i don't own the other model, that surely is much more pretty in the graphic parts and other particular functions, I was speaking of my experience with this model and VSTOL behavior.
In this case if a model it's more difficult to handle, this not specifically implies that is more accurate.
I hope to have been clear, and sorry if my english is not perfect.
 
Interesting thread. I have the Razbam harrier and wonder, if I get the simworks one, can the airfiles be swapped and work or are there to many other parameters that will keep this from working?
 
MCDesigns said:
Interesting thread. I have the Razbam harrier and wonder, if I get the simworks one, can the airfiles be swapped and work or are there to many other parameters that will keep this from working?
Click to expand...

Both models use custom simconnect DLL's for flight control, swapping the air file is not an option.
 
Ok after reading all these threads, I am interested in acquiring a harrier. I havent ever flown VSTOL simulations, so which of the two SSW or RAZBAM would be best to buy?
 
hae5904 said:
Deacon211, don't get me wrong as I only made a general statement about someone mentioning the statement of "realistic" . And as you could have read, NONE is realistic.
So post is not even close about a contest!
I only mentioned about the highter cockpit workload during a VTOL landing, and as you said you'd flown Harriers before, you actually should know that.

And again, nothing about lighten up a fire (again....way behind us).

Cheers,
Hank
Click to expand...

Sorry Hank, I just took it as a dig against those who liked the SSW model, even if it was "easier" to fly and wanted to make sure we weren't equating "harder" with "better" unduly.

If that's not what you were driving at, then I was in error for saying so.

Agree that there is no point in igniting debate about the issue and there is much to be said about both offerings. :)

Deacon
 
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