Im not talking about reading back instructions verbatum as such, just for exampple squwak codes. When say a pilot get assigned a squawk and say "roger (callsign)." And then puts the wrong squawk in the transponder. It then requires the controller to reiterate the last transmission, which in turn, as youve stated, redueces available RT time. Where as if the pilot read back squawk 1234 then the controller can hear if this is correct and the short term memory of the pilot registers this number as he/she has said it out loud.
There is no such list that I am aware of in what is called Part 91 (US General Aviation regulations) flight. There is an official US document called the Airman Information Manual, or AIM, which takes the regulations and weaves them into an aviation "best practices," or where theory and regulations meets reality. However, the AIM is NOT regulatory so recommendations within this document not specifically having to do with regulations are just that, recommendations. Note that any angry FAA official could use the "careless and reckless operation" rule to cite a pilot breaking an AIM recommendation, but that is for another thread.
The specific chapter on communication from the AIM is here:http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/Chap4/aim0402.html
The regulation that covers ATC communications for Part 91 flight is titled "Compliance with ATC clearances and instructions"
and merely states that a pilot must comply with all ATC instructions, unless an emergency exists. How the pilot acknowledges these instructions is not mandated, at least for Part 91 flight. (Note that airline operation manuals often augment FAA rules for commercial, scheduled operations and the rules specified in these manuals become regulation by the fact that they are in operation manuals, but I defer discussion of Part 121/135 - scheduled flight - for a qualified pilot).
What I was looking for ( youve said xxxx is discouraged ), was if there is an official list of read-backable itemds. ( excuse the rubbish wording ). For example in the UK we have the CAP413 RT manual, Obviously you have something similar that dictates the exact items that are required to be read back.
You aren't going to find an official list. Instead, you will find many authoritative articles written by controllers providing what they want to hear read back. Technically, a pilot could simply read back his/her tail ID to acknowledge a controller's instruction (in all cases but runway hold short instructions - a relatively recent requirement) but in cases of altitude, heading, or speed assignments this won't make the controller believe the instruction was completely understood.
The AIM stresses brevity but doesn't list what is considered crucial. From the many advanced safety articles I have read the theme is that any instruction that could potentially create a loss of separation if not properly executed should be read back. Any "informative" comment by the controller, or any instruction that would not result in a loss of separation can be handled by Tail ID, or Wilco, Tail ID. Fly in busy airspaces and believe me, this is appreciated by all on the frequency.
Consider this example:
Me: "Syracuse Approach, Bonanza XXX, level five thousand, information bravo."
Controller, "Bonanza XXX, Syracuse Approach, altimeter 29.98, turn left 250, descend and maintain 3,000, expect ILS 28 approach. You will be number three for the approach."
Me: "left 250, leaving five thousand descending three thousand, Bonanza XXX."
Note that I did not read back altimeter (since most likely I was ready for it from the ATIS) and did not read back the "expect" part, since that is merely informational and I am already expecting that given the ATIS and weather conditions.
Note also that I have adopted the "do not read back squawk code - instead acknowledge with a tail id" recommendation offered by numerous aviation magazines since I have not yet had a short-term memory issue and know that the controller will see the code appear on the scope. I do understand and agree that if the pilot finds repeating squawk codes or frequencies a memory aid, then by all means do it. Again, though, this is not mandated by any regulation.
Just for arguments sake, im not trying to suggest that pilots in the US are rubbish in any way. Every country does things differently so dont take the "lax" comment to heart. I was just pointing out that compared to Europe, the reading back of items doesnt seem to be as...critical...if thats the right word.
Ultimately im trying to learn more about the way things are done in the US. Not trying to debate who is better.
Hence my use of the words, "with respect." It is my impression that this is a civil discussion.