747400sp From United States of America, joined Aug 2003, 3883 posts, RR: 2 Posted (7 years 10 months 3 weeks 3 days 19 hours ago) and read 12891 times:
I recently saw a B 52 in action for the first time that I could remeber. When the A/C started it engines, the ground crew hook a cord or hose from an APU cart, to the number 3 and 4 engines. The pilot started the number 3 and 4 pushing them to near full power, them the ground crew unhook the cord or hose and the the pilot push the number 3 and 4 engines to near full power agine, so they could start up number 5 and 6, then the pilot push number 3,4, 5 and 6 to near full, to start up 1 and 2. Then the pilot push all running engines to near full so they could start up 7 and 8.
Is this the normal way to start up a B52, or did they do this because the base that they was visiting was a fighter base, and may not have had eough APU carts to start up all eight of this B-52H engines?
PS: I have to say, after seeing and hearing a BUFF in person. There only few word to destribe a BUFF, A CLASSIC BEAST!
Uscgc130 From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 10 months 3 weeks 3 days 5 hours ago) and read 12744 times:
It strikes me as unlikely that engines 3/4 would need to be brought upnto near full power in order to supply enough bleed air to start any ofnthe other engines. Plus, having that much asymmetrical thrust wouldnprobably place undesirable stress on the airframe.
You bring those two engines up to full power to get enough bleed air to start the other engines. I'm having a hard time picturing why all six running engines would need to be brought to full power to start the last two though.
On the KC-135A, one engine at full power could be used to provide bleed air to start the other three.
Venus6971 From United States of America, joined Dec 2004, 1453 posts, RR: 0
Reply 4, posted (7 years 10 months 3 weeks 3 days 4 hours ago) and read 12733 times:
Quoting EBJ1248650 (Reply 3): You bring those two engines up to full power to get enough bleed air to start the other engines. I'm having a hard time picturing why all six running engines would need to be brought to full power to start the last two though.
Because they started two at a time, usally at a Buff base you had a ma1a , -60, or -95 ground cart hooked to the inbd pods and started them first then you went up in power to get them at least 35 to 40 psi of bleed air to turn the the other 4 starters, the only time you used carts was during alert wartime siop or exercises, or just one engine when the pilot needed it for training. That system was mx intensive because of all the breach cleaning and continuity checks that was required.
Prebennorholm From Denmark, joined Mar 2000, 6689 posts, RR: 54
Reply 6, posted (7 years 10 months 3 weeks 1 day 18 hours ago) and read 12505 times:
Quoting Solnabo (Reply 5): Are the BUFF ever gonna swap engines ´cuz they´re to be around til 2045 according to USAF?
Huh, I could see the buff one day with four CFM56-5C4 replacing the eight PW TF-33 (the 34klbs engine used on A340-300). Also because other CFM56 versions (F108) are already in widespread use by the USAF.
But it's an awful lot of money. And the tanker replacement has higher priority and seems to last for ages.
Probably nothing will happen on the southern side of 2020. Plenty of former civil JT3Ds are sitting (or have been sitting) on KC-135Es and may "free of charge" soldier on on the buff.
But I have doubts. The TF-33 keeps its thrust much better at very high altitudes than any modern high bypass ratio turbofan engine. That may be a quality which has higher priority than longer unrefueled range.
Those birds are not flying 16 hours a day 7 days a week, so fuel cost is hardly a major consideration.
We can also hope that world peace breaks out first, and the buffs can be beercanned instead.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
KC135TopBoom From United States of America, joined Jan 2005, 12234 posts, RR: 51
Reply 7, posted (7 years 10 months 2 weeks 20 hours ago) and read 12276 times:
Quoting Prebennorholm (Reply 6): The TF-33 keeps its thrust much better at very high altitudes than any modern high bypass ratio turbofan engine. That may be a quality which has higher priority than longer unrefueled range.
That is true, low bypass engines are more effeicent at high altitudes than high bypass engines, turbojets are even better. Refueling is not a problems as long as the KC-135 is around.
Quoting Prebennorholm (Reply 6): Those birds are not flying 16 hours a day 7 days a week, so fuel cost is hardly a major consideration.
Fuel costs are a major concern. A fully loaded B-52H (with weapons) needs about 40,000lbs of fuel per hour, at cruise. When you fly from LA or ND to Guam, then Deigo Garcia, then Afghanistan, that's a lot of fuel. (total flight time from Barksdale to Deigo is 22 hours, if you go non-stop).