nelson@udel.edu (Mark Nelson) (07/08/89)
From: Mark Nelson <nelson@udel.edu> A short article in the latest _Economist_ (July 3) discussed fighter maneuverability of the F-15, F-16, Rafale (sp?), and SU-27. Apparently, the F-16 is capable of a 35 degree angle of attack, and the Rafale of 45 degrees. The article didn't mention the SU-27's sustained angle of attack capabilities, but it described the SU-27's "Cobra" maneuver: The plane, in level flight, with 0 degree aoa, pivots back to 110 degrees (beyond vertical!), and then returns back to 0 degrees, all the while travelling essentially horizontally. Anyone care to speculate on this? Does it mean the SU-27 is incredibly maneuverable? How could the plane maintain control? How does it correlate to a sustained high angle of attack capability? As a related question, how does a high angle of attack translate into greater maneuverability? My assumption is that it allows faster turns in the horizontal plane by effectively decreasing the apparent length of the fuselage perpendicular to the (vertical) axis of rotation, thereby decreasing the angular momentum of the plane. Is this right? | / Attempted diagram | / | / |/ | /| / = Fuselage of plane, length = L / | | = Axis of rotation (vertical) / | ) = Angle of Attack = A /) | - = Apparent length of fuselage normal to axis of --------- rotation = L * cos (A) Mark Nelson ...!rutgers!udel!nelson or nelson@udel.edu This function is occasionally useful as an argument to other functions that require functions as arguments. -- Guy Steele
ps01%gte.com@RELAY.CS.NET (Paul L. Suh) (07/10/89)
From: "Paul L. Suh" <ps01%gte.com@RELAY.CS.NET> >From: Mark Nelson <nelson@udel.edu> %A short article in the latest _Economist_ (July 3) discussed fighter %maneuverability of the F-15, F-16, Rafale (sp?), and SU-27. Apparently, %the F-16 is capable of a 35 degree angle of attack, and the Rafale of %45 degrees. The article didn't mention the SU-27's sustained angle of %attack capabilities, but it described the SU-27's "Cobra" maneuver: %The plane, in level flight, with 0 degree aoa, pivots back to 110 degrees %(beyond vertical!), and then returns back to 0 degrees, all the while %travelling essentially horizontally. %Anyone care to speculate on this? Does it mean the SU-27 is incredibly %maneuverable? How could the plane maintain control? How does it %correlate to a sustained high angle of attack capability? %As a related question, how does a high angle of attack translate into %greater maneuverability? My assumption is that it allows faster turns %in the horizontal plane by effectively decreasing the apparent length %of the fuselage perpendicular to the (vertical) axis of rotation, %thereby decreasing the angular momentum of the plane. Is this right? % | / Attempted diagram % | / % | / % |/ % | % /| / = Fuselage of plane, length = L % / | | = Axis of rotation (vertical) % / | ) = Angle of Attack = A %/) | - = Apparent length of fuselage normal to axis of %--------- rotation = L * cos (A) %Mark Nelson ...!rutgers!udel!nelson or nelson@udel.edu This is not terribly remarkable. F/A-18's are capable of the same sorts of stuff. Test flights have taken the Hornet to an AoA of 110 degrees in the vertical _PLUS_ 30 degrees of sideslip! (F/A-18 Hornet, by Bill Gunston, published by Ian Allan, Ltd., Shepperton, Surrey, UK (c) 1985) This is one of the reasons why the F/A-18 is being used by NASA in their high AoA test program (AvLeak, a couple of weeks ago) While I have no direct sources, I would assume that the F-16 ATFI demonstrator is capable of similar antics. Other possible candidates for aircraft capable of extreme AoA are the F-15 STOL and the X-29 Forward-swept wing testbed (I'm not sure that X-29 is the correct designation). >From what I have read, this is unlikely to become a common manuver, because it is very wasteful in energy. You go in fast, make a quick turn, and wind up going around 200 knots. This leaves you being a sitting duck if anyone launches a missile at you immediately afterwards. Not a bad thing if your fight is 1 vs 1, but in a multiple ship furball, you're a goner. VFFing in a Harrier has many of the same problems. --Paul ps01@gte-labs.com
pauls@hpnmdla.hp.com (Paul Stafford) (07/26/89)
From: hplabs!pauls@hpnmdla.hp.com (Paul Stafford) another use of high AOA could be in pointing guns during ACM. in one memorable line out of "Top Gun" ( a book) an interview with "Heater" Heatly, ACM master, in describing an encounter when he got himself very slow in an F-14 he says" for a few moments, it's like having a machine gun in a shopping cart"