Installing an Aspen E5 in a DA40 – A Case Study

by Rich Doyle, October 2023

In January, 2021 I chose to upgrade my panel to an Aspen EFD1000 E5. The modification replaces the original attitude indicator as well as the King KCS55A/KI525A HSI combo originally installed in my ‘02 DA40. It eliminates two of the aging mechanical gyros in the plane and adds some functionality, while somewhat simplifying autopilot-coupled operation. This article will discuss some details involved in getting this installation completed. While some of the hiccups noted are specific to this particular modification, others are things one might encounter with installing different kinds of avionics upgrades (Garmin G5’s, e.g.) in a DA40.

The Good News

In summary I’m totally happy with the result. Everything works as advertised. I have GPS steering, true airspeed, wind vectors, and the HSI automatically sets to the next flight segment commanded by the GNS530W. The plane will fly coupled holds and DME arcs, using GPSS “spoofing” to the KAP140 in HDG mode. With the E5 GPSS turned on, it also seems to fly approaches more smoothly.

Panel Changes

Other than the unit itself, there are a couple of changes exposed on the panel. The control switches for the original KI525A are now gone. In their place is a switch to turn the E5 on or off. And now the switch for the emergency battery control only controls the floodlight (more on this to follow).

Original HSI Control and Emergency Battery Switch
Aspen On/Off Switch and Modified Emergency Battery Placard

Now For The Complication

Aspens use a Remote Sensor Module (RSM) for certain functions. Depending on the model you choose it is a combination Outside Air Temperature (OAT) sensor, magnetometer, and GPS receiver antenna. The last is not used in my configuration but could be should I choose to upgrade to one of the other Aspen models. To properly serve all these functions it needs to be mounted on the top of the fuselage sufficiently distant from antennas and ferromagnetic material (such as cabin speakers) and must be angularly aligned fairly close to parallel with the longitudinal and lateral axes of the plane. One can choose to compromise OAT and GPS utility and mount it inside the wing or fuselage structure. Others have done that. I did not. The swooped nature of the DA40 fuselage this dictated that there be a pedestal mounted as shown to accommodate the RSM.

RSM on Custom Pedestal

The bad news is no one actually builds such a pedestal – not Aspen nor Diamond nor anyone else we could find. So it was custom-designed by the head of the avionics shop and custom-printed by a private resource he had. It was signed off by a DER he had access to. So no, I can’t give anyone a resource for it.

Shop Mistakes

I caught two significant errors the shop made and had them corrected before taking delivery:

  • The technician removed the emergency battery switch altogether. The Aspen has its own built-in standby battery so the emergency battery function is no longer needed. However, completely removing the switch disables the floodlight completely, emergency or not. I pointed this out to the technician, to which he replied (I kid you not) “what floodlight?” I showed them the unit in the glareshield, as well as the control switch and they corrected the problem. They chose to change the placard wording as noted above. I have no problem with this change.
  • The other mistake was when I went to pick it up. There was a placard that read “VFR only”. This is legitimate but ONLY if one does not retain (in my case) the visible Turn Coordinator. Of course it had to be retained in any case, as the KAP140 won’t function without it. so the placard was removed and replaced with the correct one having the admonition that the E5 rechargeable built-in battery has to be sufficiently charged to operate IFR.

There was one other omission that I came to correct myself. There is a calibration of the OAT sensor required that they either didn’t perform or did so incorrectly. This isn’t life-threatening, but does compromise the TAS and wind vector function. Directions for this calibration are in the installation manual, so I took care of it. This sensor, BTW, is a little slow to react to changes on OAT. I presume it’s due to the thermal inertia of the RSM and the mounting pedestal. This is not a big deal for its intended function, but I do rely on the Davtron if I’m concerned about rapid changes that might mean an icing risk.

A Word About Autopilots

The E5 installation manual states: The EFD1000 E5 with ACU or ACU2 emulates a Bendix King KI-525A, a NSD-360A, and a PN-101 HSI by providing outputs for HDG Datum and CRS Datum to an autopilot. The EFD1000 E5 is compatible with any autopilot that is compatible with a KI-525A, NSD-360A, or PN-101 HSI. For us, this means the KAP140, as there is no other autopilot approved for this generation of DA40’s. Currently there is great interest in having Garmin provide their GFC500 autopilot for this model. But should this come to pass, reading the tea leaves from Garmin at this point suggests the Aspen family may be excluded from controlling the GFC500 in Garmin’s STC. Instead it would require one of several competing products from Garmin.

Final Thoughts

The RSM can (and has been) installed by others in the location previously occupied by the Bendix magnetometer, inside and (inverted) outside the wing. Inside inhibits GPS antenna function and would presumably substantially compromise OAT function. Inverted outside precludes GPS antenna function, should that be desired someday. Note this admonition in the installation manual: The–003 version of the RSM is designed for inverted bottom mounting. This version may be mounted to any magnetically quiet area inside the fuselage or on the underside of the fuselage. Mounting this RSM to the underside of an aerodynamic surface, such as the wing or the horizontal stabilizer is not approved. 

The shop I used is basically local to me. It is a licensed avionics shop and supposedly a Diamond Service Center. The supervisor did do a good job coordinating with Diamond on installing that pedestal (it has to be off-center and drilling holes to mount to the shell requires a special compound to seal the edges of the holes). But neither he nor the technician doing the bulk of the installation had a clue about the emergency battery/floodlight situation. And I had to point out the VFR/IFR certification issue, which they both overlooked.

Copyright (c) Diamond Pilots Association, 2024. All Rights Reserved. Do not copy, reproduce, distribute, or republish without written permission of the author.

4 Responses

  1. For my Aspen EFD 1000 I choose to mount it in the wing where the Bendix magnetometer was previously located. This was done, in part, to avoid the problem of having to design, install and approve the pedestal. The backup VFR GPS works, but the OAT is not activated as required per the Aspen install manual. I plan to eventually install a different ACU, the ACU2, which can draw OAT data from a standard OAT probe.

  2. The Aspen is an incredibly useful upgrade to our steam gauge airplanes. We installed an Aspen Pro Max with synthetic vision, weather and traffic (from the GTX-345). Given the difficulties in mounting the RSM on the fuselage, including getting an engineering approval from Diamond to drill holes and finding a suitable mounting location or pedestal, we opted instead to mount it under the wing directly on the outboard access panel. No composite work or holes needed, and the RSM is away from sources of interference. Works like a charm.

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