It seems to be fairly well understood these days that planes have slots – it’s common for the flight crew to announce delays because the flight missed its slot or was given a bad slot. However, I’ve noticed a tendency to blame the airport, passengers mumbling about overcrowding and bad organisation. Slots are not about sharing the runway with other planes – I’ve flown from some very busy airfields including Málaga, and I have never been allocated a slot. That’s because I am VFR traffic, I fly visually and choose my route as I go, much like a sail boat. IFR flights, including but not limited to commercial passenger flights, are based on routes which they must apply for in advance and which are then approved. An IFR flight is not working on a basis of see-and-avoid and so the traffic must be managed to ensure that no two flights are at the same place at the same time. A slot time or a slot is a part of this flow management.
So if Cliff files a route to fly IFR from Málaga, he will be allocated a slot, even though he’s flying the same plane as I am out of the same airfield. He will be given specific clearance and expected to stick to his route. I am following instructions and getting permission to enter taxiways and use the runway at specific points, but I don’t have a detailed route. I am not given a slot, although I may cause someone else to miss their slot (by not getting out of the way in time).
I’ve struggled to explain this in the past (as I think you can tell) but this week I stumbled upon a perfectly brilliant explanation on the PPRuNe Forums.
A journalist asked about a rumour that an airline could not get enough ATC slots for the flights because the airline didn’t have enough staff available to man the planes due to staffing cuts. A further poster commented that an airline wouldn’t advertise a schedule unless they had already secured the ATC slots for the flights. This exhance shows fairly typical confusion regarding how slots are allocated for commercial flights. Luckily, Jumpseater came to the rescue and set everyone straight.
It seemed a shame that the guide would only be available on PPRuNe. I contacted Jumpseater, who blogs at Norven Munky’s Weblog, and he kindly allowed me to share his explanation with the rest of the world.
ATC slots are issued as a function of airspace capacity.
It’s very simple: if you have a room that holds ten idiots, you can’t put eleven idiots in the room, as much as you might like to.
Idiot number eleven has to wait until one or more idiots come out or the room is made bigger, so the idiot (No11) is given a slot time. This is the time the idiot has to present himself to commence his journey to the room.
If there’s only seven idiots in the room, then you can get three further idiots in there without restricting their progress at all, but the fourth idiot and any subsequent idiots will have to wait their turn.
If that room is in fact a corridor joining two rooms, then you can only get so many idiots down that corridor at any one time, even if the room at either end has a limitless supply of idiot capacity. Therefore any idiot wishing to pass through the corridor may get a slot time for the corridor, depending on how many idiots wish to use the corridor at any given time.
If there is another different corridor joining the rooms, you can send the idiots down those corridors, which may mean that the idiots will not be restricted at all.
So using the above Idiot’s Guide, you should be able to see that ATC SLOTS do not get secured by an airlines schedule or their staffing levels, they are a tactical daily/hourly response to airspace capacity.
On the 23rd of July 1983, Air Canada Flight 143 ran out of fuel at FL410 – 26,000 feet halfway through a 2,829 kilometre (1,768 mile) flight from Montreal to Edmonton. The Boeing 767-200 carrying 61 passengers managed to glide to safety to the Gimli Industrial Park Airport in Manitoba, a Canadian prairie province.
What went wrong? The sequence of events leading to the incident is somewhat convoluted.
The first link in the chain of events took place almost three weeks prior to the fault, on the ground in Edmonton. Boeing had issued a service bulletin for the Fuel Quantity Indicator System (FQIS) to be checked on all 767s. From an operational standpoint, the plane could not be flown if the FQIS was not functional at all, but with partial functions, the plane was considered operational but the fuel quantity needed to be measured with a float stick. The Boeing 767 C-GAUN was given a routine check by an Air Canada technician, who found that testing the three fuel quantity indicators caused them to go blank. However, during a later check the indicators worked fine.
The same technician saw the issue again, although he wasn’t aware that it was the same plane. This time he traced the problem to a faulty circuit breaker. Disabling it meant the back-up circuit breaker kicked in and the gauges worked. He pulled the breaker, tagged it as “inoperative” and apparently left a note in the log book which was not very clear.
The next day, C-GAUN flew to Montreal. Here, a maintenance worker saw the note in the logbook and checked the circuit breaker. While waiting for the fuel truck, he decided to try resetting the breaker and the fuel quantity indicators went blank. The fuel truck arrived and he got to work, forgetting about the faulty circuit breaker that he had reactivated.
This action was considered to have “contributed significantly” to the accident.
The return flight to Edmonton was a different crew. The captain noticed the blank fuel gauges and stated to the crew that they would need to perform a drip test to check fuel levels. He decided to load the full amount of fuel needed to fly directly to Edmonton with an en route stop at Ottawa to verify fuel levels.
This fuel requirement is expressed as a mass, in this case 22,300kg of fuel.
There was an estimated 7,682 litres of fuel remaining in the tanks.
The maintenance crew worked out how many litres of fuel were needed to make up 22,300kg of fuel, then subtracted the 7,682 litres on board and then used the fuel gauge on the refuelling truck to fill the aircraft tanks with the remaining required litres of fuel.
Canada was at this time changing from imperial to metric. The Boeing 767 was the first plane in the fleet to measure fuel in kilograms rather than pounds.
The maintenance crew had a multiplier of 1.77 for converting from litres. Somehow, no one noticed that this figure was for a conversion to pounds, not kilograms.
The maintenance crew calculated the amount of fuel needed using a factor of 1.77 pounds/litre rather than 0.8 kg/litre and reported that the plane had 22,300kg on board. It actually held 22,300 pounds, which is just over 10,000kg.
In the past, when fuel was calculated manually, a flight engineer’s duties included checking the fuel load. Flight engineers were a thing of the past on this 767, as a Presidential task force, under Ronald Reagan, had determined that aircraft could be built to be operated by two pilots instead of three, if the tasks previously given to the second officer (flight engineer) were either fully automated or handled by ground staff. Responsibility for ensuring adequate fuelling had passed to the maintenance branch. But because these men were not trained to calculate fuel, they assumed the pilots would make sure it was done properly.
The problem was neither of the pilots was trained in this technical task. Safety procedures had failed to keep pace with new technology. As the investigation later concluded: “Air Canada … neglected to assign clearly and specifically the responsibility for calculating the fuel load in an abnormal situation.”
The flight crew checked the figure but they only checked the arithmetic, not the conversion factor, so they came up with the same result. They manually entered the fuel amount into the flight management computer as 22,300kg. The computer tracks fuel consumption by subtracting the fuel burned from the total amount.
At Ottawa, a further drip-stick test was made and there was a further chance to spot the error. The Captain was told that the aircraft had 11,430 litres of fuel on board. He converted this using the figure that the ground crew had given him in Montreal: 1.77/litre and came to the conclusion that they had 20,400 kilos of fuel remaining. Still no one realised that the previous crew had used pounds rather than kilos. The aircraft had less than half the fuel remaining that the captain thought it did, 9,144 kilos of fuel, and nowhere near enough to complete the flight to Edmonton.
The flight crew verified the remaining fuel against the computer and took off.
When the first low fuel pressure warning sounded, the Captain believed that the left fuel pump had malfunction. He turned it off, asked for a a divert to Winnipeg and began his descent. Another low fuel pressure warning sounded, this time for the right side. Then the left engine failed, rapidly followed by the right engine.
As Pearson began gliding the big bird, Quintal “got busy” in the manuals looking for procedures for dealing with the loss of both engines. There were none. Neither he nor Pearson nor any other 767 pilot had ever been trained on this contingency. Pearson reports he was thinking “I wonder how it’s all going to turn out.” Controllers in Winnipeg began suggesting alternate landing spots, but none of the airports suggested, including Gimli, had the emergency equipment Flight 143 would need for a crash landing. The 767′s radar transponder had gone dark leaving controllers in Winnipeg using a cardboard ruler on the radar screen to try and determine the 767′s location and rate of descent.
Pearson glided the 767 at 220 knots, his best guess as to the optimum airspeed. There was nothing in the manual about minimum sink – Boeing never expected anyone to try and glide one of their jumbo jets. The windmilling engine fans created enormous drag, giving the 767 a sink rate of somewhere between 2000 and 2500 fpm. Copilot Quintal began making glide-slope calculations to see if they’d make Winnipeg. The 767 had lost 5000 feet of altitude over the prior ten nautical (11 statute) miles, giving a glide ratio of approximately 11:1. ATC controllers and Quintal both calculated that Winnipeg was going to be too far a glide; the 767 was sinking too fast. “We’re not going to make Winnipeg” he told Pearson. Pearson trusted Quintal absolutely at this critical moment, and immediately turned north.
Only Gimli, the site of an abandoned Royal Canadian Air Force Base remained as a possible landing spot. It was 12 miles away. It wasn’t in Air Canada’s equivalent of Jeppensen manuals,but Quintal was familiar with it because he’d been stationed there in the service. Unknown to him and the controllers in Winnipeg, Runway 32L (left) of Gimli’s twin 6800 foot runways had become inactive and was now used for auto racing. A steel guard rail had been installed down most of the southeastern portion of 32L, dividing it into a two lane dragstrip. This was the runway Pearson would ultimately try and land on, courting tragedy of epic proportions.
The co-pilot suspected that the Captain had not seen the guardrails nor the crowds of people. Knowing they had only one chance at landing, he decided to keep his mouth shut. Pearson came in high and fast but managed to use the rudders to lose speed and altitude in the same way as you would in a glider or small aircraft. It worked.
The rally spectators were startled to see a huge aircraft bearing down on them, silent except for the rushing of wind against its body. People scattered as quickly as they could, but only the friction between the aircraft nose and the ground as the partly extended nosewheel collapsed, brought the aeroplane to rest in front of them. The time was 2038 hours. Just 17 minutes had elapsed since Pearson had started flying a powerless 767 from 28,500 feet to a safe landing.
In 2008 the Boeing 767 was decommissioned. Its final flight is documented on YouTube:
Amazing plane, amazing story. And for people like me, flying an American plane using gallons in Europe where fuel is measured in litres, it is not a bad reminder always to check the conversions.
I only today started reading the news about the UFO over Hangzhou Xiaoshan International Airport in China. On 7 July, they had to shut down the airport after an unidentified flying object was reported above the runway. This event has dominated the news in China for the past week, with rumours ranging from Chinese military tests to extra-terrestrial visitations to a private small aircraft.
Thaindian.com has been covering the story in detail in English.
An unidentified flying object (UFO) disrupted air traffic over Hangzhou, capital of east China’s Zhejiang province, authorities said Thursday.
Xiaoshan Airport was closed after the UFO was detected late Wednesday and some flights were rerouted to airports in Ningbo and Wuxi cities, Xinhua quoted an airport spokesman as saying.
According to witness accounts and pictures of the object, it was said to have looked like a “twinkling spot” which disappeared very quickly. Stunned witnesses claim to have seen a fiery, comet-like ball in the sky, but airport workers stated that the UFO was only visible on radar and would have been impossible to see with the naked eye.
Just a few hours before the airport closing, however, many residents of Hangzhou claim to have seen a glowing object which was hovering in the sky and making odd movements. A city bus driver by the name of Yu stated that the object moved down toward the ground for about 6 minutes dragging a comet like tail, and then changed direction quickly.
The unidentified flying object sighted on Wednesday in the Chinese skies continues to baffle the officials investigating the case. After the radars picked up the object in their track path, all passengers were stopped from boarding flights. The military officials were also called for assistance by the airport authorities of Xiaoshan airport.
People’s Daily Online originally printed this photograph purportedly of the UFO in their article about the closure: Flights diverted, delayed as UFO detected hovering. You can see the image at full-size in the article.
The video above has been published all over the internet as live footage of the UFO, however it has been confirmed as a video taken earlier of a flying object which has already been identified.
The video footage is actually a “Kazakhstan UFO Video”, which was videotaped over the capital city of Bishkek, Kyrgyzstan 30th June 2010.
UFO video footage was later on identified as Russian Soyuz rocket which was blasted off on 30th June 2010 carrying a new robotic cargo ship filled with tons of supplies for astronauts living on the International Space Station.
One of the heads of China’s famous Purple Mountain Astronomical Observatory, Prof. Wang Sichao, has gone public admitting the UFOs are real and aliens are visiting Earth and that the observatory has observed their craft many times. The admittance of UFO reality was made yesterday within a official speech entitled tellingly ‘China’s UFO truth’… In the event that these aliens do not come in peace, he stressed they are not gods and have flaws and thus we can possibly defend ourselves.
I’ve yet to find a reference to this in English in any journal not specifically focused on extra-terrestrial visitations.
Bruce Maccabee takes a look at the photos and confirms that “the images are consistent with being the result of taking nighttime, ‘long’ exposure photographs of a helicopter with a searchlight”. As for what actually caused the airport shutdown, Maccabee is, like Oberg and everyone else, at a loss from the lack of reliable information. “It may have been a ‘military vehicle’ as suggested by recent stories or something else. … We may never know”.
The initial photographs in the set were taken by Frank Wandrei and Stefan Schurwanz who were taking photographs at the airport when the vintage plane lost engine power as it was coming in to land. The plane landed short on the road before the runway and then ran through a fence. There are 31 photographs in all showing the sequence of events and the after-effects. The photographs are chilling but there were no serious casualties. Only the pilot needed hospital treatment.
There’s also a video of the aftermath from the Berlin news but you are forced to watch an advertisement first.
The plane looks in a bad state although Air Service Berlin says they believe it can be made airworthy again if they can find the finance to do the repairs. Steffen Wardin told Berlin RTL, “We can not do this to history, to scrap the plane now.”
I was intrigued by the fact that the DC-3 was referred to as a “Rosinenbomber” – literally, a raisin bomber. The nickname made no sense to me, especially when I read that the plane dates from 1944 and was the last remaining flight-capable Rosinenbomber in Germany.
A raisin bomber in World War 2? What could that possibly mean?
It turned out that the nickname actually stems from 1948/49, after the war. West Berlin was under a Soviet blockade and all land routes were cut off.
However, British Commander Sir Brian Robertson offered an alternative: supply the city by air. A daunting task. Supplying the Occupation forces of 22,679 was easy, but the entire population? The only aircraft the Americans had available for the task were 5 year old Douglas C-47 Skytrains, which would only hold 3.5 tons each. After some consultation, the decision was made: it was worth a try. Earlier in April, US Forces airlifted in supplies to replace the ones being delayed by the Soviets. This was what became known as the “Little Lift”. West Berlin had two airports, Tempelhof, which was Berlin’s main airport and located in the American Sector, and RAF Gatow, in the British Sector. Supplies could be airlifted in by C-47 and there was nothing the Soviet Union could do about because, in 1945, someone had foresight. On November 30, 1945, it was agreed, in writing, that there would be three 20-mile wide air corridors providing access to the city. These were unarguable.
The initial planes were two-engine C-47 Dakotas, the military version of the DC3, which dropped coal, fuel and food for distribution, especially dried fruit. As a result, the inhabitants of Berlin took to referring to the planes as Raisin Bombers. The planes did not have a lot of storage space and so after a few weeks, the four-engine C-54 Skymaster was used instead but the Raisin Bomber nickname stuck and became the general reference for the friendly planes over the city, regardless of type or contents. The mission was referred to as Operation Plane Fare by the British and Operation Vittles by the Americans.
An American pilot is quoted in the German press as having said “Up until 3 years ago, I flew through night and fog with bombs for Berlin. Now I can come with raisins.”
In the US, the planes are commonly referred to as the “the Candy Bombers” as a result of Gail Halvorsen’s expansion of Operation Vittles.
According to Gail Halvorsen, a command pilot stationed in Germany at the time, it started when he met children watching the planes at the aiport in the American sector of Berlin. He was impressed with their bravery and wanted to give them treats but he had only two sticks of gum on him. He told them that he would drop something special just for them and they should watch for the plane that wiggled its wings before dropping its cargo.
My copilot and engineer gave me their candy rations—big double handfuls of Hershey, Mounds and Baby Ruth bars and Wrigley’s gum. It was heavy, and I thought, Boy, put that in a bundle and hit ‘em in the head going 110 miles an hour, it’ll make the wrong impression. So, I made three handkerchief parachutes and tied strings tight around the candy.
The next day, I came in over the field, and there were those kids in that open space. I wiggled the wings, and they just blew up—I can still see their arms. The crew chief threw the rolled-up parachutes out the flare chute behind the pilot seat. Couldn’t see what happened, of course. It took about 20 minutes to unload the flour, and I worried all the time where the candy went. As we taxied out to takeoff, there were the kids, lined up on the barbed-wire fence, three handkerchiefs waving through, their mouths going up and down like crazy.
Three weeks we did it—three parachutes each time. The crowd got big.
The commanding officer found out about the drops and Halvorsen thought he’d be in big trouble. But instead, the officer approved of their actions and Operation Little Vittles became official. In the end, there were 25 planes dropping dried fruit and sweets onto the city, all of which were referred to by the Berliners as Raisin Bombers.
The Rosinenbomber that crashed last month had been restored in 2000 and was used for aerial tours over historic Berlin. According to the Berlin newspaper, Gail Halvorsen – now 90 – has donated money towards the repairs of the Rosinenbomber. He wrote to the Berlin newpaper BZ saying that the plane must be made airworthy again as a visible memorial of the Soviet blockade of Berlin.
Recently I was talking to Julien of Making Time for Flying and he mentioned that his wife was from the same part of Germany as I am. He had never flown into the local airfield there and I was able to reassure him that it is a very nice airfield with easy access and friendly ATC and staff. It reminded me of an older blogpost I wrote about a staff member who was perhaps a little bit too helpful. So this week, something from the archives: Fear of Landing » Just Being Helpful originally posted in September, 2008
Cliff taxied the plane over to the pumps and I hopped out to get us some fuel.
“I’ll get out in a moment,” Cliff said. “I just want to put our route into the GPS first.”
“No problem.”
I walked over to the tiny booth behind the pumps and tapped at the door. A pale round face peered out at me.
“Hi,” I grinned. “We radio’d to say we needed some fuel?”
He chewed his bottom lip and then nodded. “How are you going to pay?”
I paused for a quarter second and he started listing the payment methods they would accept.
“Credit card,” I interjected quickly.
“We only take VISA and Mastercard,” he said with a frown.
“VISA is fine.”
“OK,” he said and finally came out of the hut. “We don’t take American Express though.”
I presumed he’d had a bad experience with a previous client. I nodded in what I hoped was a reassuring manner.
He put on a large pair of goggles and walked over to the tanks. Then he stopped and stared at the plane. I scuttled over to him.
He nodded at Cliff. “The pilot will need to disembark,” he said, distaste dripping from every word. “I can not start until he exits the plane.”
I nodded and walked to the plane to tap in the window. Cliff climbed out of the plane and then watched as the man reset the pumps. He glanced around to make sure no one was near the plane and then hooked the earth wire to the front before wandering back to the pumps to pulling the hose out.
“Could have finished by now,” muttered Cliff.
One last look around to make sure everyone was in position and finally he was ready to offer us fuel.
He filled one side and called Cliff over. He handed him the cap to screw in and watched Cliff close the tank. “You should have checked it,” he said.
Cliff looked at him blankly.
“The fuel. You didn’t check the level before closing the tank.”
“I did,” growled Cliff. The man shrugged and moved over to the other wing. He then smiled at Cliff and held up the cap.
“Check the level and then close it!”
I sniggered as Cliff stalked over and closed the tank under the man’s watchful eyes. Once he was happy that Cliff had done his job correctly, he rolled up the hose, took off his goggles and asked us to follow him to the hut.
He smiled as the credit card transaction went through without a hitch. Another potential crisis averted through proper planning. Cliff signed and we turned to go back to the plane when the man put his hand on Cliff’s shoulder.
“Your safety stickers,” he said, shaking his head. “They are old.”
Surprised, we walked out to the plane to look at our decals. They seem fine: big print stating AVGAS ONLY, a picture of a pump and Grade 100LL written underneath. Everything you need to know to to ensure someone doesn’t fill the tanks full of jet fuel.
The man waved a sheet at us with two bright red squares saying AVGAS. “It says AVGAS on our stickers already,” complained Cliff.
“Yes, but they are getting dirty around the edges. These are new.” He pressed the stickers into my hand. “You can put them next to yours if you want but I think replacing them would be better.”
I searched for a response that would get us out of here. “I will,” I told him. “But the wings are so dirty now. I will go wash the wings and put the stickers on once they are clean.”
His chest swelled with satisfaction. He patted me on the arm. “That’s a good idea,” he said and retreated back to his hut.
