Back to all transcripts
Re Solar Impulse SOLAR2 arriving Moffett NUQ
Solar Impulse 2 arrives at Moffett Field after its historic trans-Pacific flight, assisted by a relay.
Summary
This recording captures the final approach of Solar Impulse 2 (HB-SIB) into Moffett Federal Airfield on April 24, 2016, completing its perilous three-day flight across the Pacific from Hawaii. Due to communication difficulties, a military C-17 (Reach 6 Echo 1) acts as a radio relay between Oakland Center and the solar-powered aircraft. The flight concludes with warm, personal banter between the pilot and the Moffett Tower controller.
Analysis
This recording documents a pivotal moment in aviation history: the arrival of Solar Impulse 2 in California after crossing the Pacific Ocean without a drop of fuel. Because the Solar Impulse is a slow-moving, experimental aircraft that often operates at varying altitudes to manage battery power, it occasionally struggles with line-of-sight radio range. Here, Oakland Center utilizes a "Reach" flight—a Boeing C-17 Globemaster III—cruising at 37,000 feet to relay critical altitude clearances and navigation instructions to the HB-SIB pilot.
The technical core of the exchange involves airspace management. Oakland Center explains that they cannot provide an IFR (Instrument Flight Rules) clearance down to 4,000 feet because the floor of controlled airspace in that specific sector is 5,500 feet. The controller provides a "block" altitude of 5,500 to 8,000 feet, noting that if the pilot descends further, they will be outside of controlled airspace and must terminate their IFR flight plan. This highlights the complexities of integrating a unique, slow-speed experimental craft into one of the world's busiest airspaces.
As the aircraft nears Moffett Field (KNUQ), the tone shifts from formal relay procedures to a celebratory atmosphere. The Solar Impulse pilot recognizes the controller at Moffett ("Dan, nice to hear your voice, my friend"), indicating the close-knit community involved in this global mission. They joke about the PAPI (Precision Approach Path Indicator) lights and the glide slope, with the controller teasing that he is "testing the instructor" today.
The landing at Moffett Field marked the end of the ninth leg of the around-the-world trip. This specific leg was considered the most dangerous due to the lack of emergency landing sites between Hawaii and the US mainland. The successful arrival was a major milestone for renewable energy and aeronautical engineering, proving that a solar-powered plane could endure multi-day transoceanic flights.
Original ATC Communication
Plain English Translation
OAKLAND CENTER
Hotel Bravo Sierra India Bravo, Oakland Center. Reach 6 Echo 1, Oakland Center, reset transponder, squawk 2437, confirm altitude.
Reach 6 Echo 1, radar contact ten miles west of Cream. After Cream, cleared direct Sarah, direct Skaggs Island, then direct Travis. Maintain your present altitude.
Reach 6 Echo 1, Oakland Center. Reach 6 Echo 1, radar contact ten miles west of Cream. After Cream, cleared direct Sarah, direct Skaggs Island, direct Travis. Maintain your present altitude. Affirmative, and after Sierra Golf Delta, cleared direct Travis. Reach 6 Echo 1, cross Sarah at and maintain flight level 230. Reach 6 Echo 1, cross Sarah at and maintain flight level 230.
Hotel Bravo Sierra India Bravo, go ahead with your request. Hotel Bravo Sierra India Bravo, say again?
Hotel Bravo Sierra India Bravo, I’m unable to give you a clearance down to 4,000 feet. Controlled airspace starts at 5,500. You are cleared to maintain the block 5,500 to 8,000, and then you're cleared out of controlled airspace. Upon returning to controlled airspace, maintain—climb and maintain 6,000.
Hotel Bravo Sierra India Bravo, Oakland, how do you copy? Hotel Bravo Sierra India Bravo, do you hear this transmission? Ident.
Reach 6 Echo 1, Oakland.
OAKLAND CENTER
Oakland Center calling plane Hotel Bravo Sierra India Bravo. Reach 6 Echo 1, Oakland Center, reset your tracking beacon to code 2437 and confirm your current altitude.
Reach 6 Echo 1, I have you on radar ten miles west of the Cream waypoint. After Cream, you are cleared to fly straight to Sarah, then straight to Skaggs Island, and then straight to Travis. Stay at your current altitude.
Reach 6 Echo 1, Oakland Center. I see you on radar ten miles west of Cream. After Cream, head straight to Sarah, straight to Skaggs Island, and straight to Travis. Stay at your current altitude. Yes, and after Sierra Golf Delta, you’re cleared straight to Travis. Reach 6 Echo 1, cross the Sarah waypoint at exactly 23,000 feet and stay there. Reach 6 Echo 1, cross Sarah at 23,000 feet.
Hotel Bravo Sierra India Bravo, go ahead with your request. Hotel Bravo Sierra India Bravo, can you repeat that?
Hotel Bravo Sierra India Bravo, I can't give you permission to go down to 4,000 feet. The protected airspace I manage starts at 5,500. You are allowed to stay within the altitude window of 5,500 to 8,000, and then you are authorized to leave the protected airspace. When you come back into my area, climb to and stay at 6,000 feet.
Hotel Bravo Sierra India Bravo, this is Oakland, do you hear me? Hotel Bravo Sierra India Bravo, are you getting this message? Press your "ident" button so your icon flashes on my screen.
Reach 6 Echo 1, Oakland.
REACH 6 ECHO 1
Reach 6 Echo 1.
REACH 6 ECHO 1
Reach 6 Echo 1, listening.
OAKLAND CENTER
Reach 6 Echo 1, can you try air-to-air to reach Hotel Bravo Sierra India Bravo and see if you can get ahold of him?
OAKLAND CENTER
Reach 6 Echo 1, can you try a plane-to-plane radio call to Hotel Bravo Sierra India Bravo and see if you can get ahold of him for me?
REACH 6 ECHO 1
Reach 6 Echo 1, affirmative. Hotel Bravo Sierra India Bravo, Oakland Center is trying to reach you.
REACH 6 ECHO 1
Reach 6 Echo 1, will do. Hotel Bravo Sierra India Bravo, Oakland Center is trying to talk to you.
OAKLAND CENTER
Reach 6 Echo 1, thank you. Hotel Bravo Sierra India Bravo, can you hear me? Hotel Bravo Sierra India Bravo, how do you hear?
OAKLAND CENTER
Reach 6 Echo 1, thank you. Hotel Bravo Sierra India Bravo, can you hear me? Hotel Bravo Sierra India Bravo, how is my signal?
REACH 6 ECHO 1
Oakland Center, this is Reach 6 Echo 1. I'm at flight level 370, descending to flight level 230, and I got in contact with Hotel Bravo Sierra India Bravo.
REACH 6 ECHO 1
Oakland Center, this is Reach 6 Echo 1. I'm currently at 37,000 feet, coming down to 23,000, and I’ve successfully made contact with Hotel Bravo Sierra India Bravo.
OAKLAND CENTER
Reach 6 Echo 1, Roger. Can you give that Hotel Bravo Sierra India Bravo a clearance for me?
OAKLAND CENTER
Reach 6 Echo 1, understood. Can you relay an official instruction to Hotel Bravo Sierra India Bravo for me?
REACH 6 ECHO 1
Go ahead for 6 Echo 1.
REACH 6 ECHO 1
I'm ready for the message, go ahead.
OAKLAND CENTER
This is for Hotel Bravo Sierra India Bravo. Unable clearance to 4,000 due to controlled airspace. Maintain the block flight level 055 to 8,000. Cleared out of controlled airspace. Upon returning to controlled airspace, maintain the block flight level 055 to flight level 080. Go ahead.
OAKLAND CENTER
This is for Hotel Bravo Sierra India Bravo: I can't authorize a descent to 4,000 because that's below my managed airspace. He must stay within the altitude window of 5,500 to 8,000 feet. He is cleared to leave the protected airspace. Once he returns to my area, he needs to stay within the 5,500 to 8,000 foot window. Go ahead.
REACH 6 ECHO 1
Copy. Hotel Bravo Sierra India Bravo is unable 4,000 due to controlled airspace. Cleared block 055 to 080 and cleared out of block. Cleared 055 to 080.
REACH 6 ECHO 1
Got it. Hotel Bravo Sierra India Bravo, you can't go to 4,000 because of airspace rules. You're cleared to stay between 5,500 and 8,000, and you're cleared to leave that zone. Stay between 5,500 and 8,000.
OAKLAND CENTER
Okay, Reach 6 Echo 1. Good copy for Hotel Bravo Sierra India to Oakland Center. Reach 6 Echo 1, Roger, thanks. I’ve caught that. If you could also advise Hotel Bravo Sierra India Bravo that he can go below 5,500, but he will no longer be in controlled airspace. It will be off of his IFR clearance.
OAKLAND CENTER
Okay, Reach 6 Echo 1. I heard you relay that to Hotel Bravo Sierra India. Reach 6 Echo 1, thanks, I’ve got that confirmed. If you could also let him know that he is allowed to go below 5,500, but he won’t be in protected airspace anymore. He’ll be flying on his own without his official instrument flight rules protection.
REACH 6 ECHO 1
Hotel Bravo Sierra India Bravo, if you are below 055 altitude, you will be out of controlled airspace and off your IFR clearance. From Reach 6 Echo 1.
REACH 6 ECHO 1
Hotel Bravo Sierra India Bravo, if you go below 5,500 feet, you'll be out of the protected area and off your official instrument flight plan. Message from Reach 6 Echo 1.
SOLAR IMPULSE
Negative. Outside of the 055 to 080 block, you will be outside of the controlled airspace for Oakland Center.
SOLAR IMPULSE
No, that's not it. If I go outside that 5,500 to 8,000 foot window, I'll be outside the airspace managed by Oakland Center.
OAKLAND CENTER
Reach 6 Echo 1, can you confirm with Hotel Bravo Sierra India Bravo that he's going direct GOBBS right now? That’s Golf-Oscar-Bravo-Bravo-Sierra, GOBBS.
OAKLAND CENTER
Reach 6 Echo 1, can you confirm with Hotel Bravo Sierra India Bravo that he's flying straight toward the navigation point GOBBS right now? That’s Golf-Oscar-Bravo-Bravo-Sierra, GOBBS.
REACH 6 ECHO 1
Hotel Bravo Sierra India Bravo, confirm you're going to point GOBBS? Golf-Oscar-Bravo-Bravo-Sierra.
REACH 6 ECHO 1
Hotel Bravo Sierra India Bravo, can you confirm you're heading to the point named GOBBS? G-O-B-B-S.
SOLAR IMPULSE
Affirmative from Hotel Bravo Sierra India Bravo, going direct GOBBS at this time.
SOLAR IMPULSE
Yes, this is Solar Impulse, we're heading straight for the GOBBS navigation point now.
OAKLAND CENTER
Reach 6 Echo 1, Roger. Thank you so much for your help. Reach 6 Echo 1, contact Oakland Center on 125.85. Good day.
OAKLAND CENTER
Reach 6 Echo 1, I’ve got that. Thanks a million for your help. Reach 6 Echo 1, switch over to the next Oakland controller on frequency 125.85. Have a good one.
REACH 6 ECHO 1
Starting to get a little broken up. That was 125.85 for Reach 6 Echo 1?
REACH 6 ECHO 1
Your signal is starting to cut out a bit. Was that 125.85 for Reach 6 Echo 1?
OAKLAND CENTER
Affirmative, 125.85. And thank you.
OAKLAND CENTER
That’s correct, 125.85. And thanks again.
REACH 6 ECHO 1
Okay, switching to 125.85. Have a great day.
REACH 6 ECHO 1
Okay, moving over to 125.85 now. You have a great day.
OAKLAND CENTER
Trailer. Hotel Bravo Sierra India Bravo, contact NorCal Approach on 135.1. I repeat, Hotel Bravo Sierra India Bravo, contact NorCal Approach on 135.1.
OAKLAND CENTER
Alright. Solar Impulse, switch over to the Northern California approach controllers on 135.1. Repeating, Solar Impulse, contact NorCal on 135.1.
SOLAR IMPULSE
Moffett Traffic information, Hotel Bravo Sierra India Bravo, Solar Impulse staying north of the airport before integration in downwind for runway 32 left. 2,700 feet descending.
Dan, nice to hear your voice, my friend. I'm coming.
SOLAR IMPULSE
Moffett field traffic, this is Solar Impulse. We're staying north of the airport before we join the traffic flow parallel to runway 32-Left. We're at 2,700 feet and coming down. Dan, it’s good to hear your voice, buddy. I’m on my way in.
MOFFETT TOWER
Okay, very good. And I am sure you will observe the glide slope, so I don't have to remind you.
MOFFETT TOWER
Okay, sounds good. And I’m sure you’ll keep a close eye on your descent angle for the landing, so I won't even need to remind you.
SOLAR IMPULSE
I know, I know. I'm sure you chose that runway to avoid the PAPI, so you want to test me this time.
SOLAR IMPULSE
I know, I know. I bet you picked this runway just so I can't use the visual landing lights; you’re really trying to test my skills this time.
MOFFETT TOWER
Absolutely. Now we will also test the instructor, not only the student.
MOFFETT TOWER
You got it. Today we’re going to see what the teacher can do, not just the student.
SOLAR IMPULSE
Moffett information traffic, Solar Impulse Hotel Bravo Sierra India Bravo joining downwind runway 32 left.
Solar Impulse turning base, runway 32 left.
Solar Impulse turning final, runway 32 left.
SOLAR IMPULSE
Moffett traffic, this is Solar Impulse. We’re now flying parallel to runway 32-Left. Now Solar Impulse is making the turn toward the runway. Solar Impulse is on the final straightaway, lined up for runway 32-Left.
0:00
0:00