Boeingfixer From Canada, joined Jul 2005, 536 posts, RR: 0
Reply 1, posted (8 years 2 months 3 weeks 3 days 12 hours ago) and read 2749 times:
Stages are actually know as Zones. Zones are essentially separate fuel spay manifolds before the AB flame holder that allow more control over the AB power output. If less AB is required, only 1 zone could be used. As more AB power is required the additional zones will be activated by the FADEC or AB fuel control unit. Early AB's had only one stage or zone = on or off. There can be anywhere from 1 zone to 6+ zones depending on engine type.
Blackbird From , joined Dec 1969, posts, RR:
Reply 2, posted (8 years 2 months 3 weeks 3 days 4 hours ago) and read 2702 times:
To my knowledge, stages or zones on the afterburner allow more lee-way in terms of afterburner-control.
In the old days, the afterburners were basically ON or OFF, and guzzled a thousand pounds of fuel every minute. Adding some ability to have more control of the afterburner, the J-79 was fitted with a modulated afterburner with five different settings. The highest setting had the most thrust and fuel burn. The J-75, at least some models, featured a Min-AB, in addition to a Max AB setting.
The J-58 used on the blackbird, has vernier control over the afterburner; able to regulate it just like one would regulate the engine RPM.
Starlionblue From Greenland, joined Feb 2004, 17265 posts, RR: 67
Reply 3, posted (8 years 2 months 3 weeks 3 days 1 hour ago) and read 2672 times:
Quoting Blackbird (Reply 2):
In the old days, the afterburners were basically ON or OFF, and guzzled a thousand pounds of fuel every minute.
Not to mention being like an elephant kicking you in the kidneys when it was punched on.
Apart from the modulation ability mentioned above, zoned afterburners have a gentler transition from no afterburner to full (and back) is gained. This is better for both the airframe and the pilot. Note that it doesn't take two minutes, but even a subsecond zone stagger will make the transition much smoother.
"There are no stupid questions, but there are a lot of inquisitive idiots."