Difference Training GA8tc G-HTFU

Introduction

This information outlines specific training required to operate a GA8tc Airvan (G-HTFU) aircraft – CS propeller, Turbocharger and Aspen EFIS. However, it is essential to note that the UK CAA's regulations are subject to change, and it is advisable to acquaint yourself with any updates regularly. The Skyway Code, available at Skyway Code is a convenient resource for understanding the relevant information.

In case of any discrepancies between this document and the current version of the Skyway Code, the Skyway Code should be considered the authoritative source.

Difference Training

In the UK, it is mandatory to undergo differences training before assuming the Pilot in Command (P1) role in an aircraft, especially in any designated "Official Differences" categories. This training must be conducted by a Flying Instructor (FI) or Class Rating Instructor (CRI) who has already obtained the relevant "difference" sign-off themselves. The duration of training is not predetermined in terms of time or hours. Instead, it depends on the instructor's satisfaction and confidence in the pilot's ability to operate the aircraft safely. Typically, the training flight lasts for one hour from block to block, and it is recorded in the pilot's logbook as P/UT (Pilot Under Training), with the FI/CRI's name (Lewis) listed as the Pilot in Command (PIC). It is important to note that these designations are not considered ratings, although the terminology is occasionally used in casual conversations, such as referring to a "Tailwheel rating.”

Differences Categories (Non-exhaustive list)

1.     variable-pitch propeller

2.     Retractable undercarriage

3.     turbocharged or supercharged piston engine

4.     cabin pressurisation system

5.     Tailwheel

6.     Single power lever control (SPLC)

7.     Electronic flight instrumentation system (EFIS)

Electronic Flight Instrument System (EFIS)

UK CAA CAP 804 Section 4 Part H, subpart 1 page 15 (Page 277)

4.3.9 Differences training in Single Pilot aeroplanes with Electronic Flight instrumentation systems (EFIS). Increasingly, single-pilot aircraft are being fitted with digital Electronic Flight Instrumentation Systems (EFIS) consisting of electronic ‘glass instruments’ and integrated digital avionics displays of widely varying complexity and capability. These systems present a significant change from conventional, mechanical flight instruments in the way the information is presented and the interpretation of these systems requires a thorough understanding by the pilot.

For the purposes of this requirement, an EFIS display requiring differences training is an electronic presentation of the primary flight instruments that presents gyroscopic instrument, pressure instrument and navigation information that is used by the pilot as a primary reference for control of the aircraft in flight.

Differences training requires both theoretical knowledge and training on an appropriate training device or an aeroplane. The instructors and training providers who may give the training are detailed in subsequent paragraphs. Pilots converting to an EFIS equipped aeroplane for the first time, within the Single Engine Piston Class Rating, are required to complete differences training to the satisfaction of an appropriately qualified Class or Instrument Rating Instructor or Flight Instructor.

Those pilots with logbook evidence to show that they have been operating these aircraft as pilot in command prior to September 9th 2010, the issue date of an AIC on the topic, are exempt from this requirement.

Pilots converting to another EFIS equipped aeroplane within the privileges of other type or class ratings are strongly advised to complete similar differences training. When converting either to or from EFIS within a single-pilot type rating, pilots should attend a Training Organisation approved to conduct type-rating training courses on the particular aircraft type and variant.

4.3.10 Converting between different EFIS installations Pilots converting to another Integrated EFIS display should obtain further differences training, whether or not the same manufacturer produces the new system. Familiarisation training should be sufficient for FIs or CRI/TRIs who are fully qualified to teach all applied instrument flying and who are already trained on another Integrated EFIS system.

Referenced https://publicapps.caa.co.uk/docs/33/CAP804April2015REFONLY.pdf

“In short, if it’s an electronic version of the typical six-pack instruments, even if the electronic version only performs the same as the mechanical instrument, it is still classed as an Electronic Flight Instrument System (EFIS) :- Dave Lewis June 2023

G-HTFU is fitted with an Aspen Avionics EFD 1000 E5 EFIS, replacing the AI and DI. The pump was removed because these were the only two gyroscopic instruments driven by the engine-mounted vacuum pump. The Aspen E5 guide is located here E5_Dual_EFI_Pilot_Guide_4WEB.pdf

The Aspen unit is integrated with other aircraft parts, such as the Pitot line. The diagram below gives an idea of the typical setup.

To minimise potential electromagnetic interference from engine equipment and aircraft electronics, the RSM Unit is positioned at the rear of the aircraft, away from magnet sources. This location helps to ensure a quieter electrical environment for the RSM, reducing the risk of noise interference. Additionally, non-magnetic screws are utilised for the RSM and the surrounding panels to mitigate any magnetic interference. This attention to detail in the choice of materials helps to maintain the integrity and functionality of the RSM Unit by minimising the influence of external magnetic fields.

Time should be spent working through the functions and controls on the ground. We will cover the functionality to the extent we use the device and how to regain the critical displays for safe aircraft control during the training on G-HTFU.

Section 6 of the PDF listed covers all emergencies. Some basic emergency procedures are listed here.

Establishing a Frequent CROSS CHECK with alternative airspeed, altitude, and directional gauges is essential.

The E5 will run on its internal battery for approximately 30 to 60 minutes if aircraft power is lost or an over voltage is detected (33volts+).

Note: other electrical instruments slaved with the E5 will have powered down!

Electrical power loss is an emergency, and the aircraft should divert or land as soon as practical.

Terminology Definition

Land as soon as practical: expedite a landing or diversion to a suitable airfield

Land as soon as possible: The urgency of the landing is paramount. The primary consideration is to ensure the survival of the occupants. Landing in trees, water, or unsafe areas should only be considered a last resort.

Turbocharger Unit

The following covers the turbocharger unit fitted to the Lycoming 540 engine on the GA8tc Airvan (G-HTFU). Normally Aspirated Engine

Suck, Squeeze, Bang and blow

To comprehend the advantages of a turbocharger, it is necessary to grasp the contrast between a normally aspirated engine. A normally aspirated engine also called a naturally aspirated engine, relies on atmospheric pressure for intake. Adding a turbocharger to the engine can enhance the air intake and combustion process.

The air pressure and oxygen content decrease when we ascend to higher altitudes. This requires adjustments in the fuel flow to maintain optimal combustion, a process known as leaning the fuel mixture. However, as we continue climbing, there is a point where the engine becomes incapable of generating sufficient power due to the low outside pressure. The piston cannot create enough vacuum to draw in fuel, and insufficient oxygen impedes combustion. It is important to note that this power loss typically occurs after reaching altitudes above 9,000 feet and even lower on hot days.

While the technical intricacies of engine operation are more complex, the main point is that typically aspirated engines have limitations in climbing performance at higher altitudes due to reduced outside pressure and oxygen content. Pilots should be aware of these limitations, particularly when flying above 9,000 feet or in hot weather conditions.

Turbo/Super Charger

A forced induction engine integrates a turbocharger, which boosts the air mass beyond atmospheric pressure. This enables more fuel to be introduced, resulting in a larger combustion volume exerting more force on the piston. This allows us to maintain a sufficient fuel and oxygen mixture at high altitudes without relying on the piston to create a vacuum. The workings of turbocharged engines are more intricate, and I recommend conducting further research if you desire a deeper understanding.

The GA8 Turbo can produce a manifold pressure of 40 inches of Mercury (40mp). The GA8tc POH specifies a restriction of 5,000 feet of pressure altitude. Operating the GA8tc Airvan (G-HTFU) from Bridlington, we utilise 5,000 feet on the QFE, resulting in a maximum manifold pressure of 38mp.

It is crucial to note, especially for the Turbocharge endorsement sign-off, that not all turbocharged engines operate similarly. These differences entail various operating restrictions, such as time limits or combinations of manifold pressure (MP) and RPM to avoid vibrations and propeller harmonics. Always ensure you have thoroughly read the relevant aircraft's POH or sought further training before operating.

The turbocharging system is regulated to deliver an accurate fuel-oxygen mixture for optimal performance. This eliminates the need to lean the fuel intake during the climb to altitude. In fact we require a rich fuel mixture to keep the turbo and engine cool. However, during the jump run and descent, we lean the fuel to assist in controlling the cool-down process. This prevents engine warping, which can wear push-rods, valves and other engine components.

I intentionally avoid using the term "shock cooling" as it implies keeping the engine hot is necessary. In reality, the engine naturally cools down during descent. The objective is to maintain a consistent cooling process from the front to the back of the engine, preventing the cylinder heads and other critical components from warping. The EDM (Engine Data Monitor), TIT (Turbo Inlet Temperature) gauge, and cowl flaps provide enhanced temperature control, enabling us to achieve a decrease in engine temperature of around -16 during descent, with a maximum of -20, known as Cool Down (CLD).

The EDM CLD display indicates only the cooling process. If the reading shows zero, it could actually mean that the engine is heating up again. Cross-referencing the analogue cylinder head temperature gauge is a good practice during the descent as we aim to be around the 100-degree mark as you pass through 2,000 feet during descent. – external ambient temperatures will affect the numbers shown here.

Emergency procedures

In the event of a turbo unit failure, a significant loss of power and unsuitable fuel mixtures may occur for the specific altitude of the failure. However, it is possible that the engine can still generate enough power to sustain flight at lower altitudes by employing appropriate fuel mixture leaning techniques. Nonetheless, in the case of any engine failure or suspected issues, it is essential to prioritise expedited landing as soon as practicable.

The turbo unit operates using exhaust gas, and a failure in the turbo system could indicate the potential escape of hot exhaust gases into the engine compartment, which could lead to a fire hazard. For a comprehensive list of emergency procedures in the event of turbocharger failure, please consult the GA8tc Airvan Pilot's Operating Handbook (POH). During the hands-on flying of the GA8tc Airvan G-HTFU, you will receive detailed instructions on the complete operating procedures and performance specifications.

Cruising

The POH covers all cruise settings based on the fastest speed or best endurance. Any pilot looking to fly G-HTFU and not just up and down should consult the POH and landing and take-off distance requirements accordingly.

Constant speed propeller  

The constant speed propeller is often misunderstood in the aircraft community. People sometimes compare it to gears on a bicycle or car or think it boosts speed. While these descriptions may be acceptable, fully understanding the advantages and operation for safe use is crucial.

To gain a better understanding, let's consider the various propeller types found in typical single-engine piston aircraft.

Fixed-Pitch Propeller

The fixed-pitch propeller is the first type you'll encounter. These propellers are precisely matched to the engine type and available horsepower. They have an aerodynamic shape and a blade twist that compromises between the three primary flight conditions: climb, cruise, and descent. Typically, the propeller is designed to be most efficient during the cruise phase.

The details of thrust and airspeed formulas, L/D max, LRC, MRC, aspect ratio, transonic tip speed, and an optimum number of blades are beyond the scope of this discussion. Let's just say that experts have determined the best speed and blade angle to optimise engine performance, speed, and fuel consumption. I will call this "The Boffin Curve."

Variable Pitch Propeller

The variable pitch propeller allows us to adjust the angle of the blades. This adjustment can be made on the ground or using a lever with two or three different pitch settings operated during flight. A fine pitch setting reduces drag on the propeller, resulting in less workload on the engine and allowing the propeller to reach the Boffin curve quickly. This benefits short-field take-offs and climbing as we reach take-off speed quickly but provides the lowest thrust setting at higher speeds, reducing cruising speed.

On the other hand, a coarse pitch provides more thrust but takes longer for the RPM to reach the Boffin curve, resulting in a longer ground roll for take-off and a slower climb rate.

Both fixed and variable pitch propellers experience constant changes in RPM during climbs and descents. Slight climbs cause the RPM to drop, moving away from the sweet spot of the Boffin curve. Descents cause us to pass the sweet spot, all requiring throttle adjustments to compensate for these changes.

Constant Speed Propeller

The constant speed propeller, controlled by a governor, continuously adjusts the propeller's pitch angle to maintain a constant RPM, keeping us in the sweet spot of the Boffin curve. Additionally, we can control the propeller's RPM to suit our requirements, with the full range of settings available in the Pilot's Operating Handbook (POH).

Propeller over speed can occur when the RPM exceeds the red line limit. This can put excessive stress on the propeller blades and hub. Over-speed conditions can be caused by setting a lower RPM and higher manifold pressure outside the specified settings in the Pilot's Operating Handbook (POH). Overspeed can cause severe vibration, which can quickly lead to damage. To prevent a pilot-induced overspeed, a simple rule of thumb is to ensure that the throttle lever is never positioned ahead of the RPM lever.

In a single-engine aircraft, a loss of oil pressure can cause the propeller to move to the full fine-pitch position at maximum RPM. If an over-speed condition occurs, it's essential to take immediate action. Reduce the throttle settings and slightly increase the pitch of the aircraft to decrease the airspeed driving the propeller. Additionally, check the oil pressure, as it may indicate early signs of engine issues.

For a comprehensive understanding of constant-speed propellers, it's crucial to consider that each engine type and propeller combination will have specific manifold pressure and RPM settings listed in the POH for optimal performance during take-off, climb, cruise, and descent. The POH may list combinations that should be avoided due to propeller harmonics. Some aircraft show yellow bands on the RPM gauge to indicate areas where maintaining stabilised RPM settings should be avoided.

It's worth noting that constant-speed propellers may have different configurations for multi-engine aircraft, which could contradict the abovementioned information. In such cases, the POH should always be considered the authoritative source of information.

The provided notes are specifically tailored for the hands-on training of the GA8tc Airvan G-HTFU. The pilot is responsible for ensuring they are thoroughly familiarised with a different aircraft and should seek further training before flying any other aircraft types or variants.