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it takes 65% RPM to get an empty harrier to taxi


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No loadout, 100% fuel, nozzles straight back (not at 10º as prescribed by Natops). The Harrier won't start moving forward until ~65% RPM. This is for an aircraft that, according to Natops, shouldn't even be started up unless it has chocks or is tied down, because it could roll forward at idle.

Natops also suggests deflecting the nozzles 10º to reduce forward thrust at idle, and that rotating the nozzles back and forth should be enough to taxi on the ground.

 

 

I understand the issue with "sticky tires" in DCS, but the Harrier case is really extreme.

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What if the Harrier is already rolling? Will it come to a stop without braking if engine is running at idle with nozzles straight or is it enough trust to keep it rolling as per NATOPS?

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No loadout, 100% fuel, nozzles straight back (not at 10º as prescribed by Natops). The Harrier won't start moving forward until ~65% RPM. This is for an aircraft that, according to Natops, shouldn't even be started up unless it has chocks or is tied down, because it could roll forward at idle.

 

Natops also suggests deflecting the nozzles 10º to reduce forward thrust at idle, and that rotating the nozzles back and forth should be enough to taxi on the ground.

 

 

 

 

 

I understand the issue with "sticky tires" in DCS, but the Harrier case is really extreme.

I rather have it this way than sliding into aircraft or the island on a carrier deck. It is necessary to overcome inertia before a plane starts rolling. Not sure the Harrier is accurate at 60% throttle or more, but when the mass is in motion it rolls with very little power.
Edited by shagrat

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I brought the same issue up at the Tomcat subforum. It seems, that Devs could manage to get that working correct, but it would lead to a lot of other problems. The root is in DCS itself.

However, the Tomcat feels a bit better now, no idea if or what they have changed so far.

But you are right, it feels that too much thrust is needed for taxing (and keep taxing) the Harrier.

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Even loaded I use 60% to move, 40% to stay moving at a slow speed.

 

It's been a DCS issue forever. It affects every aircraft i fly. Rule of thumb, enough throttle to hear the engine start to spool keeps you moving.

 

 

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The MiG-29 doesn't have such problem at all, so I think the tools to model it properly are there.

The matter with sliding on the deck could be the real issue here (i.e. the MiG-29 is not carrier capable so who cares if it slides...). ED better do something about it, considering they are advertising the carrier dlc as the be-all, end-all of carrier simulations.

 

Anyway few patches ago the Harrier was behaving better in this regard, before Razbam changed the thrust tables for the engine.

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If you advance the throttle very slowly, you will see that you actually need about 55 - 60% to un-stick the Harrier. Just before un-sticking you can see the nose sinking from forward thrust squeezing the nose wheel shock absorber.

 

Once you are rolling, you need 45% to maintain any given speed below about 30kn, curves and wind not included.

 

IIRC the reason for 10° on the nozzles on the ground is to avoid blowing hot exhaust on the flaps only, although it is also written that while taxiing, if you find yourself moving too quickly, to increase the nozzle angle to dissipate thrust and decrease speed... of course that's in the Real-World™ where the Harrier starts rolling without brakes on with the engine at idle :doh:

 

What I've read here is basically that ED doesn't know how to simulate a wheel..... smh

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Which RPM are you guys using? External view info bar, Fan or Core RPM?

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Set the HUD master mode to VSTOL, in which case the digital RPM% is in the lower-left of the HUD just above the digital jet pipe temp.

 

Look at the EDP (Engine Display Panel) above the right MPCD, where you find the RPM shown in hundredths; eg 0920 = 9.2RPM

 

You may also find it on the ENG page in the MPCD, but I haven't looked for it specifically.

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Set the HUD master mode to VSTOL, in which case the digital RPM% is in the lower-left of the HUD just above the digital jet pipe temp.

 

Look at the EDP (Engine Display Panel) above the right MPCD, where you find the RPM shown in hundredths; eg 0920 = 9.2RPM

 

You may also find it on the ENG page in the MPCD, but I haven't looked for it specifically.

He asked which one you use, not where you can find it... I guess he does know the plane VERY well! :smartass:

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The MiG-29 doesn't have such problem at all, so I think the tools to model it properly are there.

The matter with sliding on the deck could be the real issue here (i.e. the MiG-29 is not carrier capable so who cares if it slides...). ED better do something about it, considering they are advertising the carrier dlc as the be-all, end-all of carrier simulations.

 

Anyway few patches ago the Harrier was behaving better in this regard, before Razbam changed the thrust tables for the engine.

 

I did land the Su-33 on US aircraft carrier, and the amount of thrust to roll on the deck is crazy.

It was even compressing the nose landing gear like if I had breaks on :music_whistling:

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Didn't know it is more common problem in DCS, but I always have thought that the engines are very underpowered to get an aircraft (empty, 20-50% fuel) rolling, as you often are at those 70-80% RPM to get taxiing and then around 50-60% RPM to keep it going.

 

Now how I have come to conclusion it feels that too much thrust is required to get aircraft rolling?

Because there are nice videos how F-5 etc are moved around by a few people pushing it almost effortlessly.

But then you have other things to consider, like a how I can get a 1300kg car rolling so easily just pushing it from the driver door frame when on level. Sure, slight angle upwards by couple degrees and it is totally another thing. But still, I would think that a aircraft engines will have more thrust than a one person pushing 1300kg on wheels by giving little weight on it to get it going and then keep it going is easy.

 

 

And I have wondered since I read here from the F/A-18C pilot that as you are not allowed to use engines to move on the carrier deck unless green shirt gives you the permission, it is very difficult on the current DCS to get even moving at proper speed, as you can't just quickly push little thrust to get going, pull to idle and then use inertia to perform all the turns and rolling on the deck without being a hazardous to happen for all personnel behind you.

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I did land the Su-33 on US aircraft carrier, and the amount of thrust to roll on the deck is crazy.

 

It was even compressing the nose landing gear like if I had breaks on :music_whistling:

Of course it compresses the nose strut. The thrust is applied way behind and above the nose wheel, thus a part of the force always acts downwards against the friction first... I admit the power required to overcome friction is a bit too much, but if the alternative is planes crashing into one another due to wind and creeping over the ground then exploding during startup, I prefer the current limitations... as for the AV-8B maybe Razbam needs to adjust the friction, after the recent changes in the engine model/thrust? I remember to be able to move a gunned up Harrier with 60% RPM (Engine Control Panel) and keep taxiing at around 30-35% with using nozzle position at 20-25° to reduce speed and 10° to speed up gently. Need to check this again.

Lately only flying carrier ops...

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Of course it compresses the nose strut.

No nose strut on no aircraft in the world gets compressed (at least so much that you can see it) when just applying enough thrust to taxi when no brakes are applied.

 

I admit the power required to overcome friction is a bit too much, but if the alternative is planes crashing into one another due to wind and creeping over the ground then exploding during startup, I prefer the current limitations...

I prefer fixes. Accepting and beeing fine with workarounds which make other things worse is not good. Just makes everything more and more worse.


Edited by viper2097

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I prefer fixes. Accepting and beeing fine with workarounds which make other things worse is not good. Just makes everything more and more worse.
That is if it needs "fixing". If it is a limitation of the Sim, it may not be fixable. My guess is the heavy friction has to do with the planes sliding across the decks of carriers. In MP this is a showstopper, so if a "fix" would mean we have crash carnage on carrier decks, this is a fix I am not interested in.

In the end Razbam together with ED need to see if this can be done or not.

For me this isn't much of an issue, as I never worry about the RPM display but apply thrust gently until the plane rolls and reduce throttle to an appropriate amount of thrust to keep it rolling... and honestly, in my world this is nothing I would prioritize over say JDAM implementation or adding LOFT mode... but that's just me.

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He asked which one you use, not where you can find it... I guess he does know the plane VERY well! :smartass:

 

*ahem* he asked

Which RPM are you guys using? External view info bar, Fan or Core RPM?
:doh:

When you hit the wrong button on take-off

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No loadout, 100% fuel, nozzles straight back (not at 10º as prescribed by Natops). The Harrier won't start moving forward until ~65% RPM. This is for an aircraft that, according to Natops, shouldn't even be started up unless it has chocks or is tied down, because it could roll forward at idle.

 

 

IRL the pilots always throttle up prior to taxiing in order to get the plane in motion regardless of what the loadout is. Getting 23,000+lbs of dead weight to get in motion requires significant thrust and yes, the NATOPS says not to start up without chocks or tiedowns, but that's in there for safety, not necessarily because it says it could move at idle (even though yes, that's what it says verbatim). I have found that 55-60% gets you moving , just like what

If you advance the throttle very slowly, you will see that you actually need about 55 - 60% to un-stick the Harrier. Just before un-sticking you can see the nose sinking from forward thrust squeezing the nose wheel shock absorber.

 

Once you are rolling, you need 45% to maintain any given speed below about 30kn, curves and wind not included.

 

and that is definitely high compared to real life, but not by much. Especially on a pitching and rolling LHA/D where I've seen pilots have to get up to about 65-70% to overcome a swell then immediately chop to idle and slam on the brakes so as not to overshoot the handlers commands and run into the scuppers.

 

IIRC the reason for 10° on the nozzles on the ground is to avoid blowing hot exhaust on the flaps only, although it is also written that while taxiing, if you find yourself moving too quickly, to increase the nozzle angle to dissipate thrust and decrease speed... of course that's in the Real-World™ where the Harrier starts rolling without brakes on with the engine at idle doh.gif

 

 

As far as rotating nozzles to 10 degrees or greater, it's not just about blowing hot exhaust on the flaps, which is a major reason, but IRL the jet bounces around quite extensively when nozzles are at 0 and the entire tail plane (the H-stab and the Vert-stab) shakes horribly and makes the bushings in that area wear out well before they should. Anything above 40% when at 0 on the nozzles and you can't write anything legibly on your kneeboard due to the shaking.

 

 

About the only thing outside of WIP and bugs that I have seen that is truly not modeled well is the Short Lift Wet max RPM that is attainable when you have nozzles greater than 11-14 degrees with water selected and landing gear down. All I see is max 116.8% versus the 120%(+-.2%) that current RR-F402-408 engines are able to attain. The 116.8% currently modeled was for RR-F402-406B engines that were used in the Day Attack versions. There were never ANY Night Attack aircraft that had 406B engines. Also, the ACCEL time from 60-105% is extremely fast at 0.9%, where 1.8-2.2 seconds is realistic. Sure, the EDP (or EPI, Engine Performance Indicator) does not model the BIT function even close to RL and little things like not seeing the water light (the green W on the EDP) or the left, ready, right brow refueling lights on the lights checks is pesky, but doesn't affect much other than my OCD.


Edited by vstolmech513
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IRL the pilots always throttle up prior to taxiing in order to get the plane in motion regardless of what the loadout is. Getting 23,000+lbs of dead weight to get in motion requires significant thrust and yes, the NATOPS says not to start up without chocks or tiedowns, but that's in there for safety, not necessarily because it says it could move at idle (even though yes, that's what it says verbatim). I have found that 55-60% gets you moving , just like what

 

and that is definitely high compared to real life, but not by much. Especially on a pitching and rolling LHA/D where I've seen pilots have to get up to about 65-70% to overcome a swell then immediately chop to idle and slam on the brakes so as not to overshoot the handlers commands and run into the scuppers.

 

Not talkign abotu pitching and rolling deck, I am talking about an empty airplane on a flat ramp. Fully aware that you need to throttle up to start moving (although there are many airplanes that happily start moving at idle).

 

 

 

 

About the only thing outside of WIP and bugs that I have seen that is truly not modeled well is the Short Lift Wet max RPM that is attainable when you have nozzles greater than 11-14 degrees with water selected and landing gear down. All I see is max 116.8% versus the 120%(+-.2%) that current RR-F402-408 engines are able to attain. The 116.8% currently modeled was for RR-F402-406B engines that were used in the Day Attack versions. There were never ANY Night Attack aircraft that had 406B engines. Also, the ACCEL time from 60-105% is extremely fast at 0.9%, where 1.8-2.2 seconds is realistic. Sure, the EDP (or EPI, Engine Performance Indicator) does not model the BIT function even close to RL and little things like not seeing the water light (the green W on the EDP) or the left, ready, right brow refueling lights on the lights checks is pesky, but doesn't affect much other than my OCD.

 

This is all very intersting and useful info, can you please report it in a separate thread? It's a big thing if we're getting values from a different engine than what is installed...

Also there are many posts about the fast deceleration solenoid, that have gone completely ignored.

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When the Harrier was first released it taxied at low rpm's with ease. It was changed. There is now heavy drag on the ground for taxi. Its Razbam interpretation of the AV8B taxi speed. Its not correct. The same with there switch automation that is way to slow compared to other aircraft in the DCS World.

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When the Harrier was first released it taxied at low rpm's with ease. It was changed. There is now heavy drag on the ground for taxi. Its Razbam interpretation of the AV8B taxi speed. Its not correct. The same with there switch automation that is way to slow compared to other aircraft in the DCS World.
It's not an interpretation, it is the friction against the ground so it does not slide on a carrier deck.

Likely they did not adjust it after the recent engine performance tweak.

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As you can see the Harrier taxi (AT IDLE)to a stop then bring up the throttle to taxi again. Not using 40% throttle to keep moving. Not correct.

 

Remove the drag on the ground where its not needed.

 

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