I've read that all Southwest Airlines 737-300 and 737-500 aircraft have the "hardball" panel. Was chatting with a SWA fight crew about flight simulation the other day and noticed the 733 panel was completely without EFIS. However, there was a CDU.So what is the CDU tied to for autoflight? An INS perhaps? Wish I'd thought to ask the question of the crew, but the conversation was focused on SWA procedures.Anyone have some knowledge to share on this?Jim Harnes

It really isn't about if whether the aircraft is EFIS-equipped or not. For instance, there's a full analogue MD-80, it has FMS though. I don't know how it's called on the Boeings (I believe it is IRS), but on the MD's it's called AHRS. And the aircraft has that equipment whether its instrumentation is EFIS or "steam-gauges".

It really isn't about if whether the aircraft is EFIS-equipped or not. For instance, there's a full analogue MD-80, it has FMS though. I don't know how it's called on the Boeings (I believe it is IRS), but on the MD's it's called AHRS. And the aircraft has that equipment whether its instrumentation is EFIS or "steam-gauges".

Thanks for the reply, Ed. The IRS (inertial reference system) is indeed present. Don't know if it's the same as an INS (intertial navigation system) such as the Civia, which was used prior to present day full up flight management systems.Might be dancing on the head of a pin, but I hope to understand what is feeding navigation information to the autopilots. Incidently, there is only one CDU in the SWA 733 and it's on the FO side.Jim Harnes

I've read that all Southwest Airlines 737-300 and 737-500 aircraft have the "hardball" panel. Was chatting with a SWA fight crew about flight simulation the other day and noticed the 733 panel was completely without EFIS. However, there was a CDU.So what is the CDU tied to for autoflight? An INS perhaps? Wish I'd thought to ask the question of the crew, but the conversation was focused on SWA procedures.Anyone have some knowledge to share on this?Jim Harnes

I'm not sure I understand the question.The autopilot is coupled to the CDU (FMC), which gets it's position from the IRU ("INS"[nomenclature]). Again, I'm not sure exactly what the question is, but a good deal of the "classic" seven-threes (US Airways for example) have all analog instruments. They ordered the 7-3 with analog to ease the switch from the old -200 models, plus they were the launch customer so I'm not sure if it was offered yet.Anyway, the autopilot works the exact way it would as in an EHSI/EADI ("EFIS") equipped 737 except you don't have the nifty screens to view your route. Even the MCP is identical between the digital and analog flight decks.I completely missed the question, didn't I? :( Oh well, I love the seven three and wanted to join in.

Exactly the info I'm looking for, Zack! Thought there might be some other system between the CDU and the autopilot.Am attempting to put a custom 733 panel together and wanted to get as close to Southwest as possible.Thanks,Jim Harnes

You're welcome, Jim. I almost forgot this site: http://www.b737.org.uk/flightinsts.htm