28 Dec How to Capitalize on Benefits From Helicopter Flight Training
How to Capitalize on Benefits From Part 141 and Part 61 Helicopter Flight Training
There has long been a debate on the advantages of Part 141 versus Part 61 helicopter flight training. Student pilots are confused by the differences and are therefore unable to determine how to make the most of the benefits offered by each.
The following remains the same, regardless of whether your train under Part 141 or Part 61: 1) Written tests. 2) Oral exam in check ride. 3) Flight portion of the check ride. 4) License issued.
Measurement of success is the same at both types of schools:
1) Instructors make or break the school. Knowledgeable, experienced instructors are key.
2) Some flight schools have a high dropout ratio. Successful schools should have at least 90% of the students they train attain the certificates and ratings they signed up for.
3) Aircraft maintenance is important. Students should very seldom have flight lessons canceled due to aircraft being grounded.
4) The school accident record should be zero or close to zero, indicating that the school places a high value on your safety.
On the surface, it looks like all helicopter flight schools are very similar. This is why it is so useful to understand the differences between Part 141 and Part 61.
The two biggest differences are:
1) Part 141 training requires following an FAA approved Training Course Outline (TCO) . Part 61 does not require a TCO be used at all.
2) The flight school itself and the Chief Flight Instructor have to meet stringent FAA requirements. Part 61 is not subject to these FAA requirements.
Let’s start with Part 61 helicopter training and flight schools. The majority of helicopter flight schools in the USA today are Part 61 flight schools. Many Part 61 helicopter flight schools start off with one certified flight instructor and one helicopter.
The flight instructor offers one-on-one training to prospective students and teaches the student as he or she sees fit. If the instructor is good, more students join the school and the owner purchases additional helicopters and hires more instructors to meet the demand.
There are no FAA inspections required for a Part 61 helicopter flight school. The flight school is free to train their students using their own chosen methods. They are expected to follow the rules and regulations in the FAR/AIM for Part 61 flight schools and training, but are not subject to FAA inspections to confirm that they are doing this.
Part 141 training and flight schools have to meet very specific requirements and standards. The helicopter flight school itself is issued an Air Agency Certificate when it passes the FAA inspections. Facilities and aircraft that will be used for Part 141 training are inspected. The Chief Flight Instructor is required to take an annual check ride with the FAA.
On the training side, the flight school submits a separate and distinct Training Course Outline (TCO) to the FAA for each certificate and/or rating that they want to teach under Part 141. For example, a Private Pilot TCO would be submitted.
This contains lesson plans for both Flight and Ground training. The flight school would have to submit another TCO for Instruments if they wanted to teach Instrument ratings under Part 141.
Don’t assume that a Part 141 helicopter flight school offers all their certificates and ratings under Part 141. Many only obtain FAA certification for Private, Instrument and Commercial certificates.
It takes a lot of work for the flight school to create TCO’s and to teach under Part 141. The FAA requires that the flight school keep extensive student documentation for Part 141, including very detailed information on student progress. This is great for the student. It is time consuming for the flight school.
There are a few very large flight schools that only offer Part 141 training. They have set schedules for their classes and teach many students at the same time. They also have regimented flight schedules. These few very large flight schools often have a very high ratio of foreign versus domestic students.
This is because SEVIS (Student Exchange Visitor Information System) requires that flight schools be FAA certified as a Part 141 flight school in order to apply for permission to train international students. The Veterans Association (VA) has the same Part 141 requirement for veterans to use their VA benefits.
Most Part 141 schools also offer Part 61 training for the same programs. For example, you may choose to do your Private Pilot under Part 141 or Part 61. Schools that offer both training methods provide the most flexibility to the student.
The student attending a Part 141 helicopter flight school gets all the benefits of attending a Part 141 school even if they choose to do some or all of their training under Part 61. This is due to the school being subject to random FAA inspections. They have to maintain their high standards at all times to retain their certification.
The disadvantage of Part 141 training is that the TCO has to be followed in the sequence written. Every student learns differently and some people prefer the flexibility of Part 61 training, which enables the student to cover materials in the sequence appropriate for him or herself.
This brings to light another advantage to a flight school that offers both Part 141 and Part 61 training. They will often use the TCO for your Part 61 training. This is great for the student pilot as you get the benefit of a structured Training Course Outline that is FAA certified, while at the same time being able to cover materials in the order that suits you best.
Another advantage to training at a school that offers both is that you can mix and match your training. For example, I did my Private Pilot under Part 61 as I wanted the flexibility to jump around in the curriculum. Flying instruments is very structured and is about learning procedures, so I choose to do my instrument training under Part 141. I found the structured approach and learning sequence worked really well for my Instrument training. I went back to Part 61 for my Commercial training.
Learning to fly a helicopter is fun, exciting and expensive. Learn all you can about your helicopter flight school and the programs they offer before making your final decision. Fly safe!
Helicopter Manifold Pressure and RPM Control
The manifold pressure of a piston powered helicopter is the way we tell how much power is developed by the engine. During normal helicopter flight the rotor rpm is kept constant therefore by varying the collective pitch and thereby varying both the thrust and drag produced by the blades the function of the engine is to keep the rotor rpm constant or in the normal operating range.
When flying a piston powered helicopter equipped with a governor the function of the governor is to automatically control the throttle in order to keep the rotor rpm constant so in essence the pilot only has to monitor the manifold pressure or set a specific manifold pressure to achieve a specific result. For the purpose of this explanation the result that gets referred to will be either to climb, descend or fly straight and level.
The problem that most students have is controlling the rotor rpm and manifold pressure combination in a non governor or correlator operated helicopter. The crux of the problem lies in the fact that the throttle by itself controls the rotor rpm as well as the manifold pressure and the collective by itself does the same.
For example let’s say we increase the engine rpm from 3000 to 3100 rpm by opening the throttle the MAP will also increase and let’s say it does so from 18″ to 20″ manifold pressure. Now lets say we leave the throttle alone (constant) and we pull the collective up the manifold pressure will increase because there is a linkage (correlator) between the collective and the fuel injection unit or carburettor.
However in most cases the rotor rpm will drop due to increased drag on the blades. If we push the collective down whilst keeping the throttle constant the MAP will decrease but the rotor rpm will increase due to less drag on the blades.
Now most people only focus or rather fixate on the engine and rotor rpm and chase the rpm up and down between the lower and upper red line with the throttle totally forgetting what the implications are on the manifold pressure.
For example lets assume we have a manifold pressure of 20″ but we sit with low rotor rpm, if the throttle only is opened to increase the rpm the manifold pressure will also increase lets say to 22″ thereby causing the helicopter to behave differently with this “new” power setting.
In the previous example if we wished to maintain 20″ MAP whilst increasing the rotor rpm the correct action would have been to open the throttle and at the same time lower the collective pitch lever slightly.
One way of figuring out which control to use being it just the throttle, just the collective or a combination of both is to always have a target MAP in mind to achieve a desired phase of flight. In other words if one wants to climb, descend or fly straight and level give yourself a manifold pressure value to achieve this phase of flight and then think what the effect will be on this value before one simply opens or closes the throttle.
After implementing this system for a while it will become a habit and by seeing certain combinations of rotor rpm and MAP values the right corrective action can be taken without thinking about at all.
Helicopter Anti-Torque Systems
To understand torque and its effect on helicopters we need to reference Newton’s Third Law of Motion which states for every action there is an equal and opposite reaction. Torque is a measure of how much force acting on an object will cause that object to rotate. In relation to helicopters, the engine turns the drive shaft, which turns the rotor.
This rotation causes a torque (a rotational force). If the helicopter is on the ground the friction between the helicopter’s landing gear and the surface will prevent the torque force from spinning the fuselage. When the helicopter becomes airborne the force of friction is removed and if nothing is present to counteract the torque force the fuselage will rotate in a direction opposite the rotors.
According to Newton’s Third Law, the action of the rotors creates an equal and opposite reaction (the fuselage spinning opposite the direction of the main rotors). For single rotor helicopters, counteracting the effects of torque can be accomplished in one of three ways.
The first way to counteract torque is with a tail rotor. A tail rotor is situated on the tail of a conventional helicopter. The purpose of the tail rotor is to reduce the effect of torque and the yaw motions inherit in helicopter flight. The tail rotor is comprised of two or four small airfoils that the pilot is able to control in the cockpit by manipulating the rudder (anti torque) pedals.
Helicopters that use dual-rotor systems do not require the use of a tail rotor as the two rotors are designed to spin in different directions canceling out the yaw created by one another without the need for a tail rotor.
The second way to counteract torque is with a NOTAR (No Tail Rotor) system. NOTAR is a fairly new form of anti-torque system developed by McDonnell Douglas. This system removes the tail rotor, which makes it much safer and also means less noise is generated.
In 1975 this concept was initially created by Hughes Helicopters; however it wasn’t until 1981 that a prototype helicopter made its first flight using the NOTAR system. Hughes Helicopters has since been acquired by McDonnell Douglas.
The NOTAR system uses a variable pitch fan driven by the transmission of the main rotor. This fan forces air at high speeds through the back of the craft, which creates lift and so adds to control.
As with any system, NOTAR has advantages and disadvantages. Its advantages include: Reduced noise levels – around 60% of the noise from conventional helicopters normally comes from the tail rotor.
Safety – the tail rotor striking something causes many accidents. By removing the tail rotor you remove this possibility and there is a significant reduction in the helicopter’s vibration.
NOTAR’s disadvantages are it isn’t as efficient as a tail rotor and helicopters that use a NOTAR system will have a loss of maneuverability.
The last way to counteract torque is known as a fenestron. This is actually a form of tail rotor commonly known as a Fantail. A fenestron is a tail rotor which is fitted within a housing. In application, a fenestron performs the same as a conventional tail rotor but there are design differences.
A Fenestron has between 8 and 18 blades, compared to a standard tail rotor having merely 2-4 blades and offers many advantages and a few disadvantages over a normal tail rotor.
The advantages include: Safety – these are much safer for ground operations because the tail rotor is enclosed in a housing. More protected – less likely for foreign objects to get into the tail rotor and cause damage and reduced noise.
The disadvantages include: Higher weight and higher air resistance which leads to increased fuel consumption. Fenestrons are also more expensive to produce and less efficient
Anti torque systems are vital to the safe operation of a helicopter, regardless of the type of system used.
Helicopter Cyclic Trim
Flying a helicopter with a cyclic trim is very simple provided a person understands the system and follows a couple of basic principles. One of the most basic forms of a cyclic trim system is simply two electrically driven motors that are activated by a switch located on the grip of the cyclic pitch lever. This switch is commonly known as a “Chinese hat” and is designed to be manipulated by the pilot’s thumb.
The Chinese hat can only move forward, aft, left and right so in other words no diagonal movement is possible. The switch is self centering and a very important aspect to remember is to never activate the switch whilst the cyclic friction controls are still on.
When manipulating the cyclic trim switch powers up either one of the two motors. One motor positions the cyclic control in the fore and aft position (pitching plane) and the other motor positions the cyclic control left and right the rolling plane.
For the sake of clarity and for our unfortunate friends that fly fixed wing aircraft it must be noted that no trimming is taking place on the blades itself unlike with fixed wings where the trimming takes place via tabs on the control surfaces.
So the cyclic trim system in a helicopter simply positions the cyclic control in a desired position therefore alleviating forces on the stick but it does not mean that the helicopter can be flown hands off as that requires an autopilot system which is far more advanced than the basic trim system.
The basic principle of flying with a trim system is to make a change then check, adjust and trim. For example if the speed of the helicopter needs to be increased from say 60 knots to 80 knots the first action will be to make an attitude change with the cyclic control alone by selecting a new attitude outside.
This change of attitude has to be checked at some stage when the pilot perceives the attitude for the new speed has been attained. After the airspeed indicator has settled minor adjustments can now be made to the attitude to refine the actual speed that needs to be flown.
Only now does the trim system come into play by manipulating the Chinese hat until no forces can be felt on the cyclic control. In other words the trim system should not be used to make the initial attitude change.
Most small helicopters with this form of basic trim system can be flown without using the trim but obviously a lot of forces will be felt on the cyclic control depending on the phase of flight.
The trim system can be a pilot’s biggest friend but if used incorrectly can be a worst enemy in so far as a person can trim the helicopter completely out of a desired attitude for example.
As said before the aforementioned dealt with a basic trim system as there are more advance systems for more sophisticated helicopters that incorporates Stability Augmentation Systems, Helipilots, Force Trim and Autopilots for example but the method of flying these systems apart from an autopilot in essence remains the same.
© Harry Helicopter Training Syllabus 2008