Date: 201702
Local time of day: 0601-1200
Location: DFW.Airport, TX
Light: Daylight
Aircraft: Widebody Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Initial Approach
Airspace: Class B DFW
ATC / advisory: TRACON D10
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Approach
Anomaly: ATC Issue All Types; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure
Primary problem: Airspace Structure

Narrative: Approach cleared us to a fix on the ILS. There was a break in his instructions which we thought was due to another aircraft trying to talk on the same frequency. The second part included a descent clearance which we were unsure it was meant for us. We stayed at our last assigned altitude and tried to receive confirmation on his instructions. Several calls were made; but the controller did not respond due to other aircraft talking. The frequency was super busy and then the controller scolded us for not descending and gave us a delay vector.It seemed that there were too many airplanes on the frequency. Everyone was trying to talk over everybody else and everyone was getting frustrated.


Second narrative: DFW/DAL/D10 was in a north flow (VFR conditions) during a major push with so many aircraft coming in that the TRACON was allowed to use 4 runways at DFW including the Runway 31R diagonal with no restrictions. The normal runways I assign are Runway 35C and Runway 35R but I had to come off Runway 35C so that the west feeders could use it; hence I started using Runway 31R for aircraft from the southeast and Runway 35R for aircraft from the northeast. Aircraft X Heavy was an oddball dual arrival from the southeast so before he even got to my airspace I assigned him Runway 35C; instructed him to proceed direct RAYMA and descend and maintain 7000. Then Dallas South got on the landline and pointed out a southbound turboprop off of DAL that he wanted to climb instead of leaving at 5000. I said 'okay but do you see my aircraft?' He said yes then I saw a 2nd turboprop highlighted up and climbing 10 miles south of the 1st one. I had multiple aircraft call up and a lot of blocked transmissions. Then I noticed that Aircraft X was still level at 11;000 and traffic for him was the 2nd (southernmost) turbo prop that was climbing southbound so I vectored Aircraft X to the northeast on a 040 heading and instructed him again to descend and asked him why he was still level at 11;000. He answered that there had been some confusion about his altitude and every time he asked about it he was blocked. I told Dallas South via the landline what was up to and what heading Aircraft X was on. Due to the other (1st) turboprop I had to leave Aircraft X on that 040 heading a mile or two longer than that I wanted and then vectored him to a 270 heading (left) to miss an aircraft which was descending for Runway 31R. Since Aircraft X wasn't turning very tight I told him about the traffic and turned the traffic further to the right. I had a 3 mile J-Ring up and those two aircraft got about 2.8 miles apart. In other words; because Aircraft X didn't descend he had to zig to the right to miss the two southbound turboprops that were climbing and then zag back to the left to miss the other traffic.Zig zagging a heavy aircraft through your airspace is not a recommended procedure. 20/20 hindsight I would have said unable to Dallas South's point outs but this so rarely happens as no one wants to be a jerk. He had slow traffic in the way of his turboprops way so he would have had to zig zag if I had said unable; plus he was working the DAL and DFW Runway 31R final and for some reason the DFW aircraft that I switched to him were not checking in on his frequency. Another thing that needs to be addressed is the poor radio reception we constantly get to the southeast! It's common to communicate clearly with aircraft 60+ miles to the northeast but to the southeast it can be scratchy with a weak signal both transmitting and receiving. Later I changed transmitters and the aircraft towards Cedar Creek (southeast) heard me much better. As for all of the blocked transmissions I don't really know how to stop that except to emphasize better radio frequency discipline as sometime it seems like you're having a bunch of student pilots calling up who are not waiting for others to reply instead of professional airline pilots.


Synopsis: Air carrier First Officer and D10 TRACON Controller reported that a clearance to descend was given; but due to a congested radio frequency the instruction was misunderstood.