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Not enough thrust to hover after latest update?????


CommandT
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Hey folks, what the hell happened to the Harrier lately? Set the weight to 20,300lbs (clean plane), tried to do a vertical takeoff at 320ft elevation - basically didn't have enough thrust available to takeoff. Even with water injection just baaaarely took off. What the heck happened!!! Flew the Harrier loads before. It was not like this!

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1 hour ago, CommandT said:

Hey folks, what the hell happened to the Harrier lately? Set the weight to 20,300lbs (clean plane), tried to do a vertical takeoff at 320ft elevation - basically didn't have enough thrust available to takeoff. Even with water injection just baaaarely took off. What the heck happened!!! Flew the Harrier loads before. It was not like this!


Temp? Pressure? Both will sap your thrust available. Any wind?

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14 hours ago, G.J.S said:


Temp? Pressure? Both will sap your thrust available. Any wind?

20C, ISA otherwise. No wind. 

 

So it's meant to be like this? Surely not. 

15 hours ago, TLTeo said:

 

It's been fixed, it's had way too much thrust since release

Seems crazy. I mean you can barely get off the bloody ground. And that's with being under the max weight for VTOL. I'm not sure I buy it. 

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2 hours ago, CommandT said:

So it's meant to be like this? Surely not. 

 

Yes.

 

2 hours ago, CommandT said:

Seems crazy. I mean you can barely get off the bloody ground. And that's with being under the max weight for VTOL. I'm not sure I buy it. 

 

How much under max weight?

If you can barely get off under max weight, but not when in max weight, then it is by the specs, right?

 

Harrier is not meant to take-off vertically for missions. It is short rolling and then jump in the air. 

It is the landing that is possible to be done vertically easily so you do not need long runways. 

 

I just did simple short attack mission.

3100 pounds of fuel

1x IRMAV

1x Mk-82

TPOD

Gunpod

 

Vertical wet take-off, 140 water consumed for that. 

I flew a 75 nmi total ground distance

I had two MT-LB as targets and a building (a tall tower).

 

I failed to destroy the vehicles with maverick as it hit somewhere elsewhere because I launched it so far and I didn't use narrow field of view to even try to acquire  lock, but it did damage both by 11% even by missing about 50 meters.

I completed the building attack with Mk.82 bomb dropped on the target perfectly, and it damaged both vehicles in proximity by 20% extra from 25 meters. 

 

When I landed back to base, I had 1500 pounds of fuel left. It took only 1500 pounds really to take-off, fly 75 nmi, drop some ordinance and return back to home and didn't consume any water for vertical landing.

 

If that would be a FARP/FOB operations, I was just 33 nmi (61 km) from the action.

The whole sortie took 12 minutes 45 seconds flying at 100 FFPM (gave about Mach 0.6), so from the take-off I was attacking the targets under 5-6 minutes (because I took the longer sight route instead going straight) and I was back in the base under 15 minutes from the take-off. I could have rearm, refuel in few minutes and get back. With the extra fuel, I could had a 11-12 minutes loiter time on the area (80-85 FFPM) by spending 1000 pounds for that, and that would have left me a 500 pounds extra after landing.

 

test_Harrier_3100.jpg

 

This is what Harrier does. You operate close to the enemy. You are light, you are fast, you are ready to attack the target in minutes after the plan has been approved.

So example your on ground troops finds an enemy, it can be 15 minutes from that you have plan made for the sortie, from that few minutes and you are in a cockpit taking-off.

And well under an hour from the intelligence gathering, you have already attacked the target.

 

How you would do that by a Hornet when the carrier fleet is 200-250 nmi from the coast? 

 

Harrier_fleet.jpg

In that process, there is easy to maintain constant or almost constant air support for marines on the ground. In a emergency situations you can have Harrier on site in few minutes even when they are not on station. 

 

This is what makes Harrier so cool, that you have a lot of things to do in the whole time that goes in Hornet for flying to and away from carrier. 

And if really do the fancy missions in Harrier, you don't take-off from a airbase but from the roadbase middle of nowhere hidden. You have some odd short straight road middle of the forest. 

 

People are now so custom to load Harrier with a crazy amount of weapons and fuel and then take-off vertically and land vertically as heavy because the Harrier engines were maybe 1.5-2x overpowered. 

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I would agree that it was probably overpowered before but now try setting ISA conditions at sea level at gross weight of 20,000lbs and tell me if you can hover even with the water switch on?? Because the real one should be able to. 

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Posted (edited)

Just tested it: I could perform a vertical takeoff  at 20000 wet but not dry which seems to be correct as the vertical takeoff weight at ISA is 20400 wet and 19100 dry (21000/19400 corrected hover weight).

 

So your observation of barely taking off at 20300 wet in 320 feet seems pretty close.


Edit: Data is from the NATOPS performance charts - not sure if I'm allowed to post the sheet here.


Edited by Blackeye
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Posted (edited)

Screen_210531_114029.png

It can hover with gross weight up to 22 000 lbs (well, not really at 22k, but close to it) in "default DCS weather conditions" close to sea level, and does it at norm lift wet rating. It would take off vertically at higher masses, but for some reason I was unable to set short lift wet rating during my tests (31.05.2021), engine just didn't go further than 116.8%. Is this a bug?


Edited by Aernov
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Posted (edited)
2 hours ago, Aernov said:

 engine just didn't go further than 116.8%. Is this a bug?

 

NATOPS says:

 

The maximum indicated rpm for the F402--RR--408 engine is limited to 120.0 percent due to structural limits and to 116.8 percent corrected rpm due to maximum flow limits.

RPM corrected to a standard day is referred to as corrected or non--dimensional rpm. The corrected rpm is automatically limited by DECS

 

So it seems 120% is the hard structural limit but DECS limits things futher - not sure if there are certain conditions that would increase that limit.

 

Edit: Or perhaps it's a display issue (in DCS?) as the table for the hexagon indicator has a column for corrected RPM which shows 116.8% for the 120% wet rpm: The engine DDI is supposed to display rpm and corrected rpm but they don't really match with that table (in DCS).

 

crpm.png


Edited by Blackeye
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Standard checkflight procedures require to check max RPM - 120.2% for 408 engine, and there are photos/videos with EDP RPM window wisible and showing 120%, so, I guess, it should display 120% for short lift wet rating.

Безымянный11.png

There is another issue - as far as I can tell, there are no power increase with throttle movement after engine reaches 116% RPM, you still can move throttle forward, but RPM and, it seems, power, won't rise, and there will be no "15 seconds" warning at full throttle.

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Posted (edited)

I haven't been able to find the relation between indicated and corrected fan speed but it seems that you should be able to get to 120% indicated.

 

If Razbam uses the 116.8% corrected rpm limit everywhere then it makes sense that you can't advance beyond that. Though that would be a bug IMHO - at least when it comes to the displayed values, if not their entire RPM calculation since the values displayed in the DDI don't match the table.

 

 


Edited by Blackeye
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