STO NOZ Angle: Discrepancy between NFM-000 and VMAT-203?

I've been revisiting my Harrier procedures and noticed a discrepancy between the different manuals, and I'm wondering if anyone can help clear things up. This is in regards to STOL Flaps Short Takeoff.

According to the NFM-000, the nozzle angle for a STO takeoff will be either 50° or 55° depending on your weight-to-hover ratio calculated from the charts in the NFM-400. This is mentioned on pages 2-78 and 2-82. The latter page also shows a sample VREST page displaying a nozzle angle of 55°.

On the other hand, page 2-34 of the VMAT-203 Flight Syllabus Guide says that a STO takeoff should be done with 60° nozzles. Indeed in DCS the VREST page also only shows an option of 60° no matter your weight-to-hover ratio.

My question is, why the discrepancy?

The Nozzle angle depends on many factors and can be below 60 degrees (normally the heavier you are the lower the angle will be). Sixty degrees is the maximum allowed angle for STO. In practice it is very rare to go below that anyway.

So the 50/55 angles are rarely used operationally, and thus omitted from the VMAT-203 syllabus? Instead of saying "nozzle angle -- as calculated" (like the NFM-000) it specifically says 60 degrees.

VMAT-203 syllabus sometimes differs from NATOPS. My guess is that you see anything else than 60 degrees very rarely on normal operations, and practically never during training, and thus to avoid confusion they chose to say "60 deg" in the syllabus.

Makes sense. On that note, is there any clarification on the 2° ND trim for takeoff when loaded with stores? I've noticed in our Harrier the ND trim settings for takeoff works great on a clean jet, but when loaded with bombs it produces way too much downward attitude once the wheels leave the ground.

The Nozzle angle depends on many factors and can be below 60 degrees (normally the heavier you are the lower the angle will be). Sixty degrees is the maximum allowed angle for STO. In practice it is very rare to go below that anyway.

Isn't that the other way around? :huh:

With a light loud-out, your NROS will be low. If at NROS you rotate to a high nozzle angle -- like 60° -- it will blow you off the runway like a leaf.

With a heavy load-out, NROS if you block the nozzle rotation to a low -- angle like 45° -- when you reach NROS, you will be putting more thrust into increasing speed and not into direct lift. The aircraft will accelerate quicker, but not get off the ground until wing-lift takes it off.

Isn't that the other way around? :huh:

No.

Isn't that the other way around? :huh:

 

With a light loud-out, your NROS will be low. If at NROS you rotate to a high nozzle angle -- like 60° -- it will blow you off the runway like a leaf.

 

With a heavy load-out, NROS if you block the nozzle rotation to a low -- angle like 45° -- when you reach NROS, you will be putting more thrust into increasing speed and not into direct lift. The aircraft will accelerate quicker, but not get off the ground until wing-lift takes it off.

That was my initial reaction too, but checked with an active duty Harrier pilot who confirmed what I have written above :)

BTW - I just committed Conventional T/O and STOL T/O training to RAZBAM and will make both available tomorrow, with VTOL one following few days after. All will be included with next week OB update. .

Well, I guess I have something to look forward to then :D

8< .. but checked with an active duty Harrier pilot who confirmed what I have written above :)

8<

I was just thinking, if you have the opportunity and inclination to ask your Harrier acquaintance, it would be nice to hear if AFC actually does work IRL like some here have said -- that when ON you can use stick and pedals to change A/C attitude, and that it will then remain in that attitude, until changed again, or turned OFF.

Makes sense. On that note, is there any clarification on the 2° ND trim for takeoff when loaded with stores? I've noticed in our Harrier the ND trim settings for takeoff works great on a clean jet, but when loaded with bombs it produces way too much downward attitude once the wheels leave the ground.

I’ve noticed this too. Matter of fact it should be doing the opposite. NATOPS says to guard the stick and expect to arrest the tendency of over rotation. Not under.

Sent from my iPhone using Tapatalk Pro