AV-8b Harrier IRL Operation Qestion

[rwbishUP]

Do pilots of the, AV-8b constantly have to adjust the angle of the thrust nozzles while performing VTOL? Or, is the angle set and held based on the current weight of the jet? If the pilots have to constantly tune the angle of the nozzles, why is it a separate control input? Why would the noz angle input, not be integrated into the throttle? Also, how is it that the Harrier reacts to rudder input when it's in a stabilized hover? Since there is no airflow across the rudders surface? May be stupid questions but, still gonna ask.

[G.J.S]

10 hours ago, rwbishUP said:

Do pilots of the, AV-8b constantly have to adjust the angle of the thrust nozzles while performing VTOL? Or, is the angle set and held based on the current weight of the jet? If the pilots have to constantly tune the angle of the nozzles, why is it a separate control input? Why would the noz angle input, not be integrated into the throttle? Also, how is it that the Harrier reacts to rudder input when it's in a stabilized hover? Since there is no airflow across the rudders surface? May be stupid questions but, still gonna ask.

Only a stupid question if it’s never asked . . . 
 

From a friend who flew the puffer - you set the angle for VTO, and when weight comes off the wheels, you use the puffer jets to fine tune your ascent. Transitioning to forward flight is just a case of reducing angle of thrust in step like fashion as speed increases.

There are puffer jets in both wingtips, either side of the tail, and in the nose.

https://www.centennialofflight.net/essay/Theories_of_Flight/control/TH28G9.htm

Edited June 10 by G.J.S

[Dragon1-1]

10 hours ago, rwbishUP said:

Why would the noz angle input, not be integrated into the throttle?

Because you want them separate, nozzle angle and throttle are two different controls. How would coupling them work, anyway? For VTOL, you want the throttle set fairly high, but nozzles full down. For a short landing, you need the nozzles angled, but a low-ish throttle. Not to mention VIFFing, which relies on independent nozzle control. Without a separate control, you wouldn't be able to control the jet properly.

Also, remember that the Harrier family started out in late 60s. It has spiffy color MFDs, but it's not an FBW jet. Its HOTAS is rather more limited than in a Hornet, despite looking broadly similar. Trying to have a computer of the era control the nozzles likely wouldn't be very safe.

[rwbishUP]

@Dragon1-1, I should've worded that better. I didn't mean have the nozzle angle operate along with the throttle position. I mean have the angle control integrated into the thrust lever as a thumb switch or something. But, of course the angle lever would still be there as a backup in case of a thrust lever switch failure.

@G.J.S WOW, that is crazy. I wondered if there were some type of thrust bleed that would direct a very small amount of auto valved thrust based on pilot inputs, while in VTOL arrangement. But, I had no idea and couldn't really find any data about it. Thanks for that answer.

Edited June 10 by rwbishUP

[Dragon1-1]

I think that a control on the throttle would've been clunky, plus it would have complicated things a lot. For instance, you'd probably need a motorized nozzle lever, like with Tomcat's wing sweep handle. Also, the STO stop is an important part of safely operating the Harrier, and implementing it on the throttle (or digitally) could also be complicated. Seeing as the control configuration worked just fine, this would have introduced unnecessary costs and complexity, all for a relatively minor convenience. The Harrier doesn't have a full HOTAS like Hornet or Viper do, in any case.

[AndyJWest]

Yup, like Dragon1-1 says, anything other than a simple lever (with a direct mechanical linkage) would add complexity. Remember, the basic design goes back to the late 1950s/early 1960s, with the Hawker P.1127 and Kestrel. They presumably found something that worked, and stuck with it. Given how much extra capability VSTOL adds to an aircraft, its remarkable how few changes they had to make to cockpit configuration to facilitate it. Other than the nozzle lever and STO stop, the only other 'special' control I can think of is the water switch - everything else is integrated into stick and rudder, used in the conventional sense. Simple is good.