DHC8-400 roll rate to establish bank angle
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Joined: May 2006
Aviation Qualifications: CPL
Posts: 578
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From: Australia
DHC8-400 roll rate to establish bank angle
Hi all,
I hoping there are some DHC8-400 nav system experts lurking here that may be able to shed light on an issue.
All cards on the table I am a procedure designer and we are testing an RNP-AR procedure in a DHC8-400 simulator. I have tested many RNP-AR procedures mainly in 737/A320 simulators and have not ever come across this scenario.
Scenario
The aircraft is flying along a TF leg and then flies over a waypoint for an RF leg. The maximum design speed for the RF leg is 210kt, but on profile the DHC8-400 would normally be well below this speed. For this RF leg, at 210kt, an angle of bank of about 21-22° would normally be required. The aircraft flies over the waypoint and overshoots the RF turn resulting in a high bank angle of 30° to re-intercept the RF leg. In the process blowing out to 1/2 scale deflection for the RF leg.
Clearly this is not ideal. However, I have noticed that it takes an unusually long period of time to establish the bank angle. And this extra time is what is allowing the aircraft to drift so far off track. It has been observed to take about 8-9 secs. The RF leg roll rate is assumed to be 5°/sec, so this bank should be established by 5 sec max. And this is what I have seen in 737/A320 simulators. The RF leg in question is immediately prior to the final approach fix.
For clarity, at profile speed it seems to execute the turn satisfactorily. But it’s making some people nervous.
Does anyone know of there is a default roll rate on the DHC8-400 at certain segments, that might be causing it to take so long to establish bank? I’m hearing rumours of an operator in Canada that may have observed similar behaviour. Any help, guidance and wisdom that can be provided would be greatly appreciated.
Cheers
Alpha
I hoping there are some DHC8-400 nav system experts lurking here that may be able to shed light on an issue.
All cards on the table I am a procedure designer and we are testing an RNP-AR procedure in a DHC8-400 simulator. I have tested many RNP-AR procedures mainly in 737/A320 simulators and have not ever come across this scenario.
Scenario
The aircraft is flying along a TF leg and then flies over a waypoint for an RF leg. The maximum design speed for the RF leg is 210kt, but on profile the DHC8-400 would normally be well below this speed. For this RF leg, at 210kt, an angle of bank of about 21-22° would normally be required. The aircraft flies over the waypoint and overshoots the RF turn resulting in a high bank angle of 30° to re-intercept the RF leg. In the process blowing out to 1/2 scale deflection for the RF leg.
Clearly this is not ideal. However, I have noticed that it takes an unusually long period of time to establish the bank angle. And this extra time is what is allowing the aircraft to drift so far off track. It has been observed to take about 8-9 secs. The RF leg roll rate is assumed to be 5°/sec, so this bank should be established by 5 sec max. And this is what I have seen in 737/A320 simulators. The RF leg in question is immediately prior to the final approach fix.
For clarity, at profile speed it seems to execute the turn satisfactorily. But it’s making some people nervous.
Does anyone know of there is a default roll rate on the DHC8-400 at certain segments, that might be causing it to take so long to establish bank? I’m hearing rumours of an operator in Canada that may have observed similar behaviour. Any help, guidance and wisdom that can be provided would be greatly appreciated.
Cheers
Alpha
