10

Pretty much what the title says. What is the purpose of the TSR-2's anhedral wingtips? I've heard someone say that they use it to counter yawing I think but is this the true reason or is it something else?TSR-2 front profile with wingtips visible

Machavity
  • 5,993
  • 2
  • 28
  • 57
BryBuriya
  • 307
  • 1
  • 7
  • Although it looks cool it's one of the few airplanes I wouldn't want to fly. Something about it makes my spider sense tingle. – GdD Feb 06 '23 at 09:02

1 Answers1

13

In the document "TSR2 with Hindsight", a lengthy documentation of TSR2 development by the Royal Air Force Historical Society, the reason given for the wingtip anhedral is the correction of lateral and longitudinal stability. Being a high-wing design, the anhedral was used to lower the sideslip-induced rolling moment.

To quote from TSR2 with hindsight:

At re-freeze, the wing was moved, its planform changed slightly and the tips given anhedral to reconcile lateral and longitudinal stability requirements; a very complex joint rib resulted. The wing already had a centre-line joint but only after great resistance from the weight-saving auditors.

The re-freeze in turn was the result of supersonic wind tunnel testing in 1960:

It was not until March 1960 that supersonic wind-tunnel test results were again available and one effect of the resultant design re-freeze was further refinement of the rear fuselage lines.

Turning down wingtips had been employed before in a high-wing design where re-designing the complete wing had been out of the question: The Heinkel 162. Here, the name for that modification was "Lippisch-Ohren" (Lippisch ears) after the person who had proposed them first for his delta-winged designs.

Peter Kämpf
  • 231,832
  • 17
  • 588
  • 929
  • So if I follow right, they're there to stop the plane from pitching up and down and rolling where they don't want it. – BryBuriya Feb 06 '23 at 09:07
  • @PeterKämpf How does wingtip anhedral affect longitudinal stability? – Aditya Sharma Feb 06 '23 at 09:56
  • 1
    @AdityaSharma I was wondering myself, I guess it affects pitch moments at high AoA. Planform changes are more effective and I think the change was mostly about dihedral effect. – Peter Kämpf Feb 06 '23 at 10:55
  • @AdityaSharma: obviously via "longitudinal dihedral" – sophit Feb 06 '23 at 11:35
  • @AdityaSharma moves the Neutral Point aft for both the longitudinal and vertical axis I would say. – John K Feb 06 '23 at 13:40
  • @PeterKämpf the CL-214 water bomber uses similar tips for the opposite purpose,to restore dihedral effect degraded by the fin-like nacelles of the PW-120 turboprops, which had an effect like changing from high wing to mid wing. – John K Feb 06 '23 at 13:44
  • Remember the anhedrals are put on the tips of a delta wing They will help bottom lift there, moving the center of lift aft as AoA increases. This is essentially how a tail responds to an unwanted pitch-up. Once the "longitudinal dihedral" does its job setting wing AoA, all forces are in balance for a given airspeed. If sudden headwind gust pitches the nose up, the anhedralled wing tips adds to the effect of the horizontal stabilizer to prevent the elevator (or pilot) from overpitching the aircraft. – Robert DiGiovanni Feb 06 '23 at 14:25
  • @RobertDiGiovanni This would make sense at supersonic speed, but given that the TSR2 was already stable at subsonic speed, there was no need to increase longitudinal stability at supersonic speed. – Peter Kämpf Feb 06 '23 at 22:47
  • @JohnK Intresting. Is there a neutral point for vertical axis? and which direction is considered "aft"? – Aditya Sharma Feb 06 '23 at 23:13
  • So, as ever, its a "fix" for a design issue that could not be resolved easily any other way. Same reason that the F-4 Phantom has turned up wings and turned down tail planes - to fix the poor aero dynamics of the design. – Moo Feb 06 '23 at 23:39
  • Yes because static stability in the pitch and yaw axis are the same thing, "weathervaning" about the CofG into the airstream, except in pitch you have to include trimming forces to vary the weathervaning target angle. If NP is the point at which all aerodynamic forces are focused, and it needs to be aft of the C of G for the weathervane (static stability) effect to work, the vertical profile of the wing tips, being aft of the C of G on a delta would increase yaw static margin slightly by moving the vertical aerodynamic center aft, and the plan area would increase pitch static margin slightly. – John K Feb 07 '23 at 01:21