Skywagon 185
Air Traffic Control Fully Certified
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem
Aircraft; Airspace Structure; Chart Or Publication; Human Factors
I was working a Cessna 185 at 5000 feet northwest bound. I called Approach to coordinate 5000 feet; and they approved it. I started the handoff and shipped the aircraft over to Approach where they accepted the handoff. Where Approach is placed there is about a 10-mile gap from Approach airspace to Canadian airspace so I knew I would have to be the one to coordinate something with Canada. I called Canada about 10 minutes later to coordinate the altitude. They approved the altitude of 5000 feet and explained that they couldn't see the aircraft on radar and because he was so low they wouldn't be able to talk until he was closer in. Their instructions were to terminate radar with the aircraft and tell the aircraft to contact center 50 miles southeast of where the aircraft was landing.I called to forward that information with Approach. They acknowledged they had all the information. I had left the data block up on my radarscope the entire time the aircraft was under Approach airspace to remind myself of the coordination needed. After coordinating with Approach; I started to notice the aircraft began a descent. I waited to see if it was a mistake and decided to call Approach to make sure the aircraft's descent was noticed by them. They told me they assigned the aircraft 4100 feet as a final altitude (even after I explained I had already coordinated 5000 feet with the Canadian sector). 4100 feet is the MSA (minimum safe altitude) in that area; but the next MSA along the aircraft's route was 4800 feet. I explained that to Approach and told them they needed to climb the aircraft back to 5000 feet. Approach tried to get a hold of the aircraft multiple times on Guard frequency and relaying through other aircraft; but they had no luck of getting the aircraft since they already shipped him. [Aircraft] entered the 4800 foot MSA at 4100 feet being a NORDO aircraft. After multiple tries on my guard frequencies and relaying through my aircraft with no luck of getting a hold of [of the aircraft]; I called Canada ATC to explain what happened and asked them if they could try to relay one of their aircraft. They did get a hold of the NORDO aircraft and climbed him to a safe altitude.Approach disregarded my instructions to keep aircraft level at 5000 feet. Approach never coordinated an altitude change. They had already shipped the aircraft off their frequency by the time I called to ask about the aircraft's descent. The aircraft flew in unsafe/unknown terrain for 10 minutes. This is a serious job. Pilots rely on us for safety; and in this situation; it is ATCs` fault that aircraft was put in an unsafe situation. Luckily everything was fine but in the future never disregard coordination or ATC instructions.
A Center Controller reported the Approach Control descended an aircraft to a different altitude than what was coordinated which placed the aircraft below the Minimum Safe Altitude.