Crossover Speed
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Crossover Speed
Hi all, I have a question for all you people out there who are smarter than me.
I completed my first jet type rating this past September and it was on the 737 (200). As it is known that the type has suffered a few accidents due to rudder hard over it is part of our sim training to train this manoeuvre.
In the aircraft ops manual there is a blurb about Crossover Speed. Now I had heard of this term before and indeed it applies to all aircraft but my question (s) is this.
Is there a formula for determining what the speed will actually be? Specifically for the 737 if that makes a difference.
If the formula is one that would require a calculator is there a quick way of getting a ruff number? i.e: 250 kts IAS = 2500 Lbs FF per eng, or mach .74 = Alt x 2 + 20 made into the EPR. That kind of thing…
What, if any are some of the factors that affect it? ( other than how far the rudder displaced ) although the statement says full rudder input and I am sure ( but could be wrong ) things like weight and air density would make a difference also.
I will include the statement from the manual for those out there that may not know what I am asking about, and to make sure it is actually correctly worded.
Crossover Speed is the speed that requires FULL lateral roll control from ailerons & spoilers to counter roll due to Yaw caused by FULL rudder input. At speeds less than crossover speed with FULL rudder input the roll induced by the rudder starts to exceed the lateral control authority of the ailerons and spoilers.
Cheers all and have a great day.
I completed my first jet type rating this past September and it was on the 737 (200). As it is known that the type has suffered a few accidents due to rudder hard over it is part of our sim training to train this manoeuvre.
In the aircraft ops manual there is a blurb about Crossover Speed. Now I had heard of this term before and indeed it applies to all aircraft but my question (s) is this.
Is there a formula for determining what the speed will actually be? Specifically for the 737 if that makes a difference.
If the formula is one that would require a calculator is there a quick way of getting a ruff number? i.e: 250 kts IAS = 2500 Lbs FF per eng, or mach .74 = Alt x 2 + 20 made into the EPR. That kind of thing…
What, if any are some of the factors that affect it? ( other than how far the rudder displaced ) although the statement says full rudder input and I am sure ( but could be wrong ) things like weight and air density would make a difference also.
I will include the statement from the manual for those out there that may not know what I am asking about, and to make sure it is actually correctly worded.
Crossover Speed is the speed that requires FULL lateral roll control from ailerons & spoilers to counter roll due to Yaw caused by FULL rudder input. At speeds less than crossover speed with FULL rudder input the roll induced by the rudder starts to exceed the lateral control authority of the ailerons and spoilers.
Cheers all and have a great day.
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Is there a formula for determining what the speed will actually be? Specifically for the 737 if that makes a difference.
If the formula is one that would require a calculator is there a quick way of getting a ruff number? i.e: 250 kts IAS = 2500 Lbs FF per eng, or mach .74 = Alt x 2 + 20 made into the EPR. That kind of thing…
What, if any are some of the factors that affect it? ( other than how far the rudder displaced ) although the statement says full rudder input and I am sure ( but could be wrong ) things like weight and air density would make a difference also.
Crossover Speed is the speed that requires FULL lateral roll control from ailerons & spoilers to counter roll due to Yaw caused by FULL rudder input. At speeds less than crossover speed with FULL rudder input the roll induced by the rudder starts to exceed the lateral control authority of the ailerons and spoilers.
Cheers all and have a great day.
If the formula is one that would require a calculator is there a quick way of getting a ruff number? i.e: 250 kts IAS = 2500 Lbs FF per eng, or mach .74 = Alt x 2 + 20 made into the EPR. That kind of thing…
What, if any are some of the factors that affect it? ( other than how far the rudder displaced ) although the statement says full rudder input and I am sure ( but could be wrong ) things like weight and air density would make a difference also.
Crossover Speed is the speed that requires FULL lateral roll control from ailerons & spoilers to counter roll due to Yaw caused by FULL rudder input. At speeds less than crossover speed with FULL rudder input the roll induced by the rudder starts to exceed the lateral control authority of the ailerons and spoilers.
Cheers all and have a great day.
Unload.. increase speed and roll wing level. And if you're below about 1000AGL, be prepared for a VERY exciting ride.
There is no formula for calculating the crossover speed, but fortunately the TP’s at Boeing have experimented and found them for you. “Them” because it is not a single speed it depends upon configuration, loading etc. They are in the range of 170-190Kts so don’t worry about calcs with Mach or FF!
The speeds are in the range were you are using flap 2 to 10, which is why back in 2000 the block speeds for these settings were increased by 10kts to increase your margins (and also why flap 2 disappeared from use). If you fly at the standard flap speed schedule it will never be an issue. If you find yourself slower than the flap speed schedule and with full rudder applied, you really need to accelerate asap otherwise you may lose directional control.
Description & background available at http://www.b737.org.uk/rudder.htm
S&L
The speeds are in the range were you are using flap 2 to 10, which is why back in 2000 the block speeds for these settings were increased by 10kts to increase your margins (and also why flap 2 disappeared from use). If you fly at the standard flap speed schedule it will never be an issue. If you find yourself slower than the flap speed schedule and with full rudder applied, you really need to accelerate asap otherwise you may lose directional control.
Description & background available at http://www.b737.org.uk/rudder.htm
S&L
Last edited by CaptainSandL; 17th Nov 2006 at 12:47. Reason: Added flap 2 info
The Boeing 737-200 FCOM displays a Bulletin that lists the cross-over speed history including a table of appropriate speeds versus flap settings and weights. In short, the design of the 737-100 and 200's means these types do not have a crossover speed limitation - unless the rudder pressure reducer modification is either not installed or unserviceable - which where reference to the revised speeds is needed. So you can relax when flying a serviceable 737-100 or 200. Not so the Classics where crossover speeds are published. I think my statement is reasonably accurate but reference to the Boeing published FCOM (not necessarily the company published FCOM!) and associated Flight Manual should confirm.
