IAS Hold Question

[Wink207 78]

Hi all:

Just a quick question, probably a quick answer will do it. 🙂 I use the IAS constantly in climb out and it works fine. However my question is on the transition from IAS to Mach. There is a knob low on the pilot's panel which can be used to change the left PFD marked speed from IAS to Mach. And there is a Mach Hold button next to the throttle synch button on the center panel. I formed the opinion that the knob and Mach Hold button could be used to switch the hold speed to Mach, and then to make adjustments. However, It doesn't seem to work that way. I cannot find any way that causes the AP to hold Mach during climb.

Please tell me what I am doing wrong.

Thanks

Rick

Edited February 4, 2019 by Wink207

[richjb2 195]

Rick,

I don't know about Carenado's implementation of the DA50EX or the real DA50EX; however, based on my experience in DA2000 Falcon, MACH HOLD next to the throttle is a cruise feature that will adjust the engine's DEECs to maintain the current MACH speed within 0.01M.  It's a poor man's autothrottle.  

Both DA2000 and the CL30 that I fly have this MACH HOLD feature, and it's a function of the engine's digital computers taking the MACH reading from the ADCs. The range of operation is limited, either to 0.01M to 0.02M.  Slight temperature variations tend to kick it off, which I don't use it very much.  Other pilots I fly with do use it with varying degrees of success. 

When you switch the PFD airspeed tape from IAS to Mach, unless you have a separate MACH button on the Flight Guidance Panel, you would use IAS button to set the flight director & autopilot to fly pitch to maintain Mach or IAS.  

Our department had a DA50 with the Proline 21 upgrade, which they called the DA50E.  I flew the DA2000 with the Proline 4.  Both of these airplanes had FLC instead of the IAS button, so this might be a Carenado implementation. 

Don't know if this helped.

Rich Boll

[Wink207 78]

Thanks Rich. Very helpful. I did misspeak about the IAS function. On this F50E it is FLCH, rather than IAS, but the same comments hold. The FLCH function is based on IAS and has no automatic or manual switch over to Mach. So I have been doing as you described, watching the tape as the Mach increases and fiddling with the speed wheel to lower the FLCH speed to control the Mach. This is all on climb as I use V/S exclusively on the descent and adjust the throttles to maintain speed. I was hoping the Mach Hold button would convert FLCH to Mach but your explanation clears that question. I do notice that the throttles are very easy to synch on this aircraft so maybe there is some sort of DEEC or FADEC code running in the background to synch the throttles. This Carenado add on flies very well and the ground handling is among the best out there. Do you do sim Rich and do you own this aircraft? It's great to hear RW experience.

Thanks again

Rick

Edited February 4, 2019 by Wink207