Airspeed Indicator

Airspeed Indicator

Air News On Air Ambulance ,Scheduled Flying Doctor Service By Soth African Red Cross By Pilatus-12NG

The KWAZULU-Natal branch of the South Africa Red Cross Air Mercy Service (RCAMS) operates a 24-hour air ambulance service and a scheduled Flying Doctor Service (FDS) out of its Durban base using three Pilatus PC-12 aircraft.

In total ,the Red Cross Air Mercy Service uses seven PC-12s in South Africa because the organization has found the type to be the ideal aircraft for use in the aero-medical field, especially in Africa  and specifically in KZN where the runways are sometimes little more than a strip of short, rough veldt.

The original PC-12 was certified in 1994 with the most recent upgrade, the PC-12 47E NG (next generation) officially launched in 2007. The Red Cross AMS has been using the PC-12 since 1996 and recently added the NG to its operation thus making it necessary for all the AMS Pilatus pilots to undergo conversion training to the PC-12NG.

I joined pilots Dave Doull and Stephan Coetzee on an FDS flight to Creighton, a small Village in the KZN Midlands, with Doull in the right hand seat as pilot instructor while Coetzee went through the conversion to the PC-12s system.

The pilots elected to fly the first leg, since it was short, at low level. Usually the PC-12NGs CPCS (cabin pressure control system) automatically sets cabin pressure in flight, using the FMS data on ICAO-registered flight management system (FMS) ,the coordinates and elevation needed to be manually entered for the correct destination location and elevation (3400 feet) .Cabin pressure, on the older PC-12s,is manually controlled.

In addition, because the flight was low level to an unknown airfield, the terrain advisory and warning system (TAWS) had to be inhibited prior to arrival at Creighton or it would have provided unnecessary loud warnings for avoiding terrain that showed no runway in the database.

On arrival at Creighton, as part of his training, Coetzee used the angle of attack indicator rather than the airspeed indicator to select the best, safest, speed for the approach and landing on Creighton's short,uphill,runway.The AOA indicator, when centered ,displays 30% speed above the stall speed at the engine power and flap setting selected at the time. This allows for very accurate and safe approach speeds, in calm conditions.

Creighton's grass landing strip is, by AMS rural KZN standards, near perfect. The weather on this day was, however, not perfect. The weather on this day was, however, not perfect, with a cold front approaching and the cloud base at 1200 feet above ground. Landing on the grass, with the uphill slope, and using the beta range on the propeller (neutral thrust position), Coetzee brought the aircraft to a taxi speed in less than 300 metres and taxied to the end of the runway at the top of the hill.

After the medical crews had disembarked we took a few minutes for photographs before seeking the shelter of the cabin-it was very cold and windy.

Before leaving Creighton, the pre-flight took a little longer than usual since the flight-plan had to be keyed into the FMS. The principle (in terms of pilot workload) of an FMS is to increase workload at easy stages of flight (pre-departure and cruise) so that the pilots workload is reduced during critical phases (IFR departure and approach) ,thereby allowing greater situational awareness.

It also allows for published procedures to be programmed to the autopilot from the FMS datadbase, thereby reducing the human errors found when manually setting up frequencies, directions, turns and altitudes.

Although Coetzee is an experienced PC-12 pilot, this was the first time he had flown the PC-12NG with the state-of-the –art Honeywell Primus Apex cockpit which, in appearance, is vastly different to that of the older PC-12.

Fourteen Stages

There are 14 stages for normal flight operations in the PC-12s Pilots Operating Handbook, from pre-flight through the flight to landing and shutdown, which a PC-12NG pilot must conduct for safe operation and each stage, might have anything from four to fifty items to check.

This workload is assisted by an electronic checklist which, with the general cockpit layout on the PC-12NG, facilities, a user-friendly cockpit flow pattern. This, said Doull, still impressed him, even though he had spent a lot of time using the aircrafts glass cockpit.

"When Honeywell and Pilatus designed the NG cockpit, they used a primary and secondary FOV (field of view) from the human eye to decide what information and controls to group and where. They also used basic colours and shapes to display the information. This has resulted in a cockpit that is easy to look at-neat and uncluttered-where critical information such as airspeed, turbine temperature, etc.is easy to find.

"And, most importantly ,it is a cockpit that when something is out of limits or is going wrong, it is easy to identify where the problem is, such as an aural stall warning accompanied with yellow/red airspeed indication, a flashing "stall " on the artificial horizon and the control yoke shaking," he said.

The PC-12NG cockpit consists of four 260 mm display screens, two of which are primary flight displays (PFD) and two are multifunctional displays (MFD).The MFDs, are situated in the top and bottom centre consoles, and display both the system screen (landing gear, flaps, fuel, electrical, systems settings, crew alerting system, CPCS) and the situational awareness screen (interactive navigation moving map, navigation log, waypoint list, Jeppesen charts etc).

The situational awareness screen has, on the map, the flight plan, geographical data, airspace and geopolitical boundaries and can have the traffic collision avoidance system, lightening strike system and weather radar overlaid.

A great function is the Jeppesen chart view, which displays the Jeppesen airway manual charts and overlays and position of the aircraft during the instrument approach, departure (SID) or arrival (STAR) phases.

"No more outdated, torn or lost paper approach plates; it is electronically updated system(every 14 days) and when you fly the approach  you get to see your aero plane on the approach plate,' Doull added.

The two PFDs (pilot and co-pilot) operate off two separate channels of information as back-up .All critical information such airspeed, altitude, is displayed on the ADI (altitude director indicator).

Engine instrumentation (temperature, torque and pressures), multi-mode digital radio system (communications, navigation and transponder equipment) and horizontal situation indicators (course deviation indicator, terrain advisory and warning system and traffic collision avoidance). Information is on the MFDs and PFDs and is accessed and programmed by use of a multi-function controller, which incorporates an alphanumeric keypad and joystick situated at the centre of the console below the MFDs.

En Route

With the flight plan stored in the FMS and the start-up checks complete, Coetzee turned the aircraft around to face the runway .The takeoff would be downhill and with the cool temperature, light load and 30-degree Fowler flap setting; the PC-12NG was airborne halfway down the 800-metre runway.

Out of Creighton and back among the clouds, it was snowing at 5000 feet –perfect, since after going through the checks and flows again the operation of the de-icing systems had been Coetzee next task.

To put the de-icing system to the test he activated the electrically heated windshields, propeller boots, and static port, Pitot tube and angle of attack probes to melt off the ice. When he noticed a moderate ice build-up he activated the pneumatic system which includes inflatable de-ice boots on the leading edges of the wings and horizontal stabilizer. Inflating and deflating these boots break up any ice accretion.

The engine anti-ice systems include the engine air-intake lip being permanently heated with hot turbine exhaust gases, to stop ice adhering and ,as an extra measure, Coetzee made sure that the inertial separator was open to pass all heavy objects (debris,ice,birds,etc) to clear of the compressor intake.

As soon as the attitude and speed correction system reacted to Coetzee having activated the engine and propeller anti-ice systems, it "assumed" ice had built up on the wings (distributing airflow) and it went into "ice mode, "providing stricter stall protection.

In ice mode, the stall protection system activates eight degrees angles of attack (on the AOA vane) lower than normal.

Next on the list, was FMS programming and auto-flight control system(AFCS) operation for the three-NDB cloud break procedure at Pietermaritzburg; this was achieved by programming the arrival phase of the FMS o insert the approach as well as manually turning the radio beacons.

The autopilot (AFCS) then followed instructions from the FMS and, in terms of vertical navigation, followed the altitude instructions set by Coetzee.

The aircraft can fly the entire three NDB approach and missed approach procedures in NAV mode on autopilot. Coetzee had only to watch the aircraft follow the Jeppesen chart and FMS information, and input the next altitude into the autopilot. This allowed him to keep his attention on the basic flight information, the terrain warning system and aircraft configuration.

According to Doull: "The high level of situational awareness afforded by the system makes for a comfortable, but aware, pilot during a complex phase of flight in very poor visibility," he said, adding:" The three NDB approach is probably the most complex IF approach in South Africa because of the numerous beacons, altitudes and headings, yet when flying the approach retrieved from the FMS database, it is a relatively simple affair."

However, because of the large amount of automation ,there was a tendency for pilots to forget basic things, said Doull,such as setting the correct power at the bottom of s descent; or coming down to the MDA (minimum descent altitude) of 3000 feet (588 feet above the runway elevation), with the flap and landing gear creating lots of drag.

"Knowing when and how much power to apply for level flight is a seemingly obvious task –but it can be simple omission in an automated cockpit," he said.

At the "missed approach" point of the procedure, Coetzee looked up to see the runway. He disconnected the autopilot, set landing flap, called ATC and slowed the aircraft down to approach speed on the AOA indicator.

Just before crossing the threshold of the runway he retarded the power lever to idle and flared for a smooth touchdown, a few seconds later, on Runway 16, bringing us safely to our destination at Pietermaritzburg.

 

About the Author

Anthony Juma is the Editor and Senior Aviation Director at Wings Over Africa Aviation. 
This is an Air Charter Company that specializes on Air Ambulance Charter  & Emergency Evacuation Flights In Kenya,Tanzania,Uganda,Rwanda,DR Congo, South Sudan,Somalia,Eastern,Central & Southern Africa The website has guided thousands of travelers to achieve their dream holiday. For more information and guidance, visit the site at http:// / www.wingsoverafrica-aviation.com/index.php/services/air-ambulance-and-medical-evacuation.html

question for instrument-rated pilots (preferably a CFII)?

when it comes to pitot-static failures, i understand that;
a) if the pitot ram air hole becomes blocked, the airspeed indicator will drop to zero; and
b) if the entire pitot apparatus becomes frozen/blocked, the airspeed indicator will essentially become an altimeter (assuming the static port still works).
what happens if the pitot tube drain hole freezes/clogs, but the ram air hole and static port are still functioning? what will the airspeed indicator show?
Richard - huh?......

Low and Slow I think you need to reread the question. None of your answers address - Ram air is free, static is free, only the drain being plugged.

As Ben Dere stated the brief time that only the drain is blocked it would not be noticeable. The amount of air "escaping" out the drain hole is not enough to affect the ram air being directed further into the pitot tube so the drain being plugged and that air that would have exited out the drain hole now going the same route as the rest of the air into the pitot tube is negligible.

Furthermore in the event that enough moisture was entering the pitot tube to create a blockage in the drain hole it is within a short amount of time plug the rest of the tube - so the likelihood of flying with only the drain plug plugged I would say is next to nil, unless it was purposely done to the pitot tube.

Airspeed indicator