Crosswind

[M016576]

Erik- the F-18 and F-15 stall at a fairly wide airspeed band based on gross weight, which is why we fly AoA approaches for both, rather than computed airspeed. The F-18 can fly controllably past the lift limit of the aircraft due to the digital fly by wire flight control system, and the F-15 has a fairly complex wing design, sweep and a mechanical flight control system backed up with a computer aided system, pitch boost compensator and aeilron rudder interconnect. With that said...

FA-18a-d approach speed at 8.1 true AOA, between 135-160kts

FA-18EF- 8.1 true AOA, 124-140kts

F-15C- 21 units (roughly 10 degrees true), 145-165kts

The biggest issue with a high crosswind in all jets is more that the Wing has a tendency to lift up and require some extra aeilron into the crosswind to keep the jet tracking, but due to the ARI, the rudders and subsequently nose steering can come into play. It can get you into PIO if you're not careful. It was a lot easier in the Navy when they turned the runway into the wind for me!

[aviatoreb]

Erik- the F-18 and F-15 stall at a fairly wide airspeed band based on gross weight, which is why we fly AoA approaches for both, rather than computed airspeed. The F-18 can fly controllably past the lift limit of the aircraft due to the digital fly by wire flight control system, and the F-15 has a fairly complex wing design, sweep and a mechanical flight control system backed up with a computer aided system, pitch boost compensator and aeilron rudder interconnect. With that said...

FA-18a-d approach speed at 8.1 true AOA, between 135-160kts

FA-18EF- 8.1 true AOA, 124-140kts

F-15C- 21 units (roughly 10 degrees true), 145-165kts

The biggest issue with a high crosswind in all jets is more that the Wing has a tendency to lift up and require some extra aeilron into the crosswind to keep the jet tracking, but due to the ARI, the rudders and subsequently nose steering can come into play. It can get you into PIO if you're not careful. It was a lot easier in the Navy when they turned the runway into the wind for me!

 

Hi Jobe,  Thanks.  Thanks for that.  I didn't expect you could say those actual numbers but I am glad you could and did since I have been curious for a long time.  So thank you.

 

I knew you land by AoA in practice which makes sense since such a large percentage of your take off weight changes due to fuel and payload changes as compared to our little airplanes, but I am surprised to see 8.1 written in tenths.  I knew that about aircraft carriers that they steer into the wind so that the airplanes can always land with direct head wind.

[jetdriven]

Large transport jets use AoA for landing as well. Depending on weight you might have a V_REF  of 125 knots, or 160 knots. In the "steam gauge" models, we took our landing weight and flap setting, looked at a flip card, and it gave you the speed. Glass airplanes know your weight so you simply confirm the V_REF for landing. But in any case, you always have a 3 degree nose-up pitch attitude on final (model specific), because the AoA is constant for all landings.  . We just don't read it directly.

 

You can also do this in a Mooney as well. Don Kaye has a real good formula for a Mooney, based on landing weight.

[Piloto]

One of the problems with high cross winds is the possibility of weather vane into the wind and side exiting the runway, specially on icy narrow runways. To prevent this I come a little bit faster on the flare (77kts) and retract the flaps completely just before (3ft) touchdown. This assures a firm grip on the runway with no porpoising on the roll out. It works very well specially in gusty conditions were porpoising is more prone to happen.

José

[M016576]

Hi Jobe,  Thanks.  Thanks for that.  I didn't expect you could say those actual numbers but I am glad you could and did since I have been curious for a long time.  So thank you.   I knew you land by AoA in practice which makes sense since such a large percentage of your take off weight changes due to fuel and payload changes as compared to our little airplanes, but I am surprised to see 8.1 written in tenths.  I knew that about aircraft carriers that they steer into the wind so that the airplanes can always land with direct head wind.

The 8.1 true alpha is a function of the hornets and super hornets digital fly by wire flight controls, which allow for a very specific and tight control of the angle of attack. The AoA for that approach is also optimized for carrier arrestment (hook to eye and hook to main langind gear distance/angle). The eagle is more traditional in nature and is a mechanical flight control system with a computer aided control system... On that jet you shoot for a single cockpit unit of AOA as opposed to a degree of true AOA (which only a flight control computer could allow you to manipulate with a linear control input across the wing's entire envelope). Most of the general operating numbers (approach speeds, landing, endurance) are unclassified in nature, once you start talking about max performance, things change a bit!

[aviatoreb]

Very interesting!  Thanks Jobe.  I figured you couldn't tell us everything and I wasn't expecting you would be allowed to tell us that much.