Plastic Pilot

Here are three weather reports (a.k.a. METARs) I got from www.easymetar.com. The first one if from New-York JFK, the second Geneva, and the third from Moscow Domodedovo. They all contain the same information: wind, visibility, clouds, temperature, and pressure. Unless you’re a pilot used to fly on various continents, something should surprise you.

KJFK 291751Z 15013KT 10SM FEW050 SCT100 BKN140 BKN250 28/18 A2982

LSGG 291820Z VRB06KT 9999 FEW050 FEW060TCU FEW070CB 29/15 Q1017 NOSIG

UUDD 291800Z 24002MPS 6000 BKN023CB BKN100 14/14 Q1004 TEMPO TSRA

Winds for New-York and Geneva are given in knots (KT), but Moscow ones are in meters per second (MPS). Good pilots know that 1 meter per second is 1.94 knots… pragmatic pilots call that 2. The other look in Google.

Then come the visibility. 10 Statute Miles (SM) in New-York, 9999 meters (10 km or more) in Geneva, and 6000 meters in Moscow. Funny to see that wind New-York is given in Nautical Miles per hour (knots), and visibility in Status Miles. And what about Geneva ? Wind in knots, visibility in meters. One must give that to the Russians, they’re more coherent: both wind speed and visibility are given in meters.

But when it comes to clouds cover… all three airports report them in feet ! Brilliant harmony, but not for long. The New-York air-pressure (QNH) is given in inches of mercury, whereas both Geneva and Moscow report it in millibars.

This simple example is just scratch on the surface of the units chaos that exist in aviation. Airspeed indicators can be graduated in knots, MPH, or kilometers per hour. Depending which manufacturer publish them, weight and balance sheets can be in kilograms or pounds. Fuel can be delivered in liters or US gallons. For larger aircrafts, it comes in tons or pounds. Oil comes in liters, or US gallon quarters.

Take-off and landing performance calculations can be critical. The tools (tables or graphs) used to determine the required distance for taking-off or landing produce results in meters… or in feet.

When it comes to flying, the things could also get complex. In Russia, altitudes in clearances are given in meters. Jeppesen publishes charts with values in feet, with conversion tables. A typical Moscow departure initial climb clereance is 3550 feet, corresponding to 900 meters.

How safe is such a unit mixture ? For a crew operating under normal conditions, this requires some additional attention. Put some extra-pressure (bad weather, technical problem, may be an emergency), and this is one more possible trap. Units problems were a contributing factor in several accidents, including the infamous Gimli Glider - a 767 that ran out of fuel at 41′000 feet, partly because of a metric units problem.

The problem is clear, so what about the solution ? Glass cockpit systems can switch between various units, reducing the number of calculations to be made by the crew. This is a good step, but not yet a full solution. So here comes the quesiton again: should aviation switch to the metric system ?

This switch would impact an incredible number of areas. On aircraft side, it means avionics upgrade, fuel system upgrade, new weight and balance documents, updates to the aircraft manuals, and probably pilot training. On ground, ATC systems shall be adapted to display speeds, altitudes, winds, pressures in metric units. Controllers shall be trained to new procedures with metric values. Maintenance engineers, fuel and dispatch staff shall also be familiarized with the new units systems.

The cost of such a switch would be simply huge. The next problem is to manage the transition. The whole aviation system could not be adapted overnight. Handling that mixed situation safely would not be an easy thing. How many Gimli-glider-like accidents could this change create before all crews get used to the new system ?

To me, it all boils down to two questions:

• Will airlines pay for this change ?
• Is the solution more hazardous than the problem ?

My crystal ball is undergoing maintenance right now, so I can’t answer those questions. If yours is working, I’d be glad to know your predictions.

PS: Many thanks to Paul from www.askacfi.com, who asked this question in a comment on his own blog.

London City Airport is on the list of my aviation projects and dreams. I love this airport, because of its a time saver, because it has a unique implantation, and because of the unique scenery it offers. However, this is for me kind of a Forbidden Land, because of all the constraints.

No private pilot can land there. No single engine (even single engine turbine) can land there. No private traffic can use this airport. All pilots operating there need to go through a special training. As I don’t want a job as professional turbine pilot, the chances for me to land there otherwise than as an airline passengers are low, if not inexistant. By the way, if you’re working for BAA / CAA and can arrange an exception (even a single ILS approach with go-around will do), or for an operator and can arrange a jumpseat flight, you’re welcome.

Before someone makes it possible for me to go there, here are some pictures, found on airliners.net. Click on them to see the full size version on airliners.net.

On this first photo, taken on final 28 on the glide path - it seems high, but look at the PAPI - one can see the construction works left of threshold. Note that the only possible way for departing aircraft is to backtrack ruwnay, and this seriously reduces the airport capacity.

The second photo, taken in 2008, shows the reason for these works: a partial parallel taxiway has been built. It is still necessary to back-track, but two planes can depart rather quickly one behind the other, and that shortly after a landing, making the runway capacity higher.

Finally, a photo taken on final for runway 10. It was also taken before the construction of the floating taxiway. The approach angle is also impressive, but the departure (go-around) path is much clearer than on runway 28…

PS: simple visit of the tower would be fine as well

The number of technical equipments needed to keep the whole aviation system running is impressive. The typical break-down is known as CNS, standing for Communication - Navigation - Surveillance. Communication includes radio and telephone, but also IT networks. The Navigation part is made of approach equipments (ILS), and en-route navigation beacons (VORs). Surveillance includes radar and other ways to detect aircraft positions.

On top of that comes the data processing system for flight plan and surveillance data, which builds the synthetic view displayed to air-traffic controllers. Airport specific systems include power, conditioned air and fuel delivery to aircraft and runway and apron lighting. Handling companies also depend on these systems to know where and when the airplanes they have to care for will arrive.

Behind all these systems is also a common infrastructure, providing essential services: power, air-conditioning, heating, backbone communication systems, building security, access control, and so on. All the safety relevant systems are doubled, if not tripled, and procedures exist to safely handle traffic in case of equipment failure. The whole system is usually quite resistant, and failures usually leads to delays, diversions, and flight cancellations. These are certainly annoying, but not dangerous.

When discussing with airport staff what would be the worst failure, the answer is always the same. Passenger Information Systems. You know, the nice displays indicating at which counter check-in takes place for each flight, and from which gate each flight will depart.

A complete loss of electrical power is normally not possible, as different power sources are available, including own generators. Moreover, power distribution is segmented so that even if a part of the airport loose power, it will not affect all of it.

A complete loss of flight information display could quickly lead to a cahotic situation. Un-informed passengers would ask the ground personel. If no information is availalbe, it could be possible to send passengers to the right terminal - most airlines always operate from the same terminal, but that’s it.

Once there, the passengers would be left with no information. Assuming that sufficient ground staff is available (not exaclty obious…), and that pilots know where to park their planes, the number of not reaching the gate on due time would create massive delays.

I saw once in Frankfurt a day where the system used to print the boarding passes was inoperative. All the rest was working find. Staff at the check-in counters printed boarding passes without gate numbers, and were sending passengers to counters in the correct terminal. Displays were giving correct information, but boarding passes had to be re-printed locally before boarding.

This “simple” problem created an average delay of more than 30 minutes ! Frankfurt being the hub of Lufthansa, the impact of these delays could be felt throughout all Europe. The problem got solved within less than one hour, but the delays persisted all day long, as they were too long to be compensated for in flight.

A complete failure of the whole passenger information system would have the same results, but at a more larger scale ! Even the problems with the new Terminal 5 in Heathrow would look as minor glitches in comparison.

Do you feel like doing a small experiment ? Next time you go through an airport, try counting the number of flight information displays you see. You’ll quickly understand why they are so imporant.