Day 4 of Ground School – Rotors, Safety of Flight, Controlled & Uncontrolled Airspace – Part 13

guimbal31Lots to cover from this class.  There’s  a couple different rotor systems in that picture to the right so we’ll start with that.

There are basically 3 systems that mean something to us, fully articulated, rigid, and semi-rigid.

Fully articulated rotors has blades that are attached to the hub through hinges that let the blade move independently. These rotor systems usually have three or more blades. The Guimbal has an articulated 3 blade rotor.

Rigid rotor system are simpler than a fully articulated rotors. Loads from flapping and lead/lag forces are accommodated through rotor blades flexing, rather than through hinges. These blades are super tough and I think that’s what the redbull helicopters have.

Semi-rigid rotors have two blades that meet just under a common flapping or teetering hinge at the rotor shaft. If you yank down on one end of the blade the other will rise.  R22s have these types of rotors.

We spent some time on flapping and feathering then moved into dissymmetry of lift. The technical definition is Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters in forward flight.

To go a little deeper … When dissymmetry causes the retreating blade to experience less airflow than required to maintain lift, a condition called retreating blade stall can occur. This causes the helicopter to roll to the retreating side and pitch up (due to gyroscopic precession – there is a great video HERE). This situation, when not immediately recognized can cause a severe loss of aircraft controllability. SO you’re about to have a real bad day. Dissymmetry is countered by “blade flapping”: rotor blades are designed to flap – lift and twist in such a way that the advancing blade flaps up and develops a smaller angle of attack, thus producing less lift than a rigid blade would. There is a great video of a hind rotor doing something close.  I’ll look for it, but the short of it is, the retreating blade flaps down and develops a higher angle of attack grabbing more lift.

…might have gone a little deep on rotor systems but it all needs to be said.  I stayed away from flapping and feathering.  I’ll get into that when I snap some pictures of the rotor on the guimbal.


On to safety of flight.

Basically you scan EVERYTHING with a series of short regularly spaced eye movements. Ten degrees every second or so is a good rule of thumb for daytime flying.

We also learned about who has the right of way.  The less control you have in an aircraft the more right of way you have.  Helicopters have lots of control so we yield to most folks.  There is much more to it but for now we’ll stick with that.

Regarding altitude… well, there are more rules around this then I have time to type.  I’m not sure I understand them all yet because you have so many different airspaces.  Which is a nice segue. KCPS, which is where I’m training is a class D, but an extremely busy class D from what I understand.


Controlled airspaces!

This is awesomely confusing and complex. It’s going to take me reading and re-reading to get this down.

Airspace ChartThis is straight from wiki!!

With some exceptions, Class A airspace is applied to all airspace between 18,000 feet (5,500 m) and Flight Level 600 (approximately 60,000 ft). Above FL600, the airspace reverts to Class E. The transition altitude is also consistently 18,000 feet (5,500 m) everywhere. All operations in US Class A airspace must be conducted under IFR. SVFR flight in Class A airspace is prohibited.

Class B airspace is used to control the flow traffic around major airports. The airspace is charted on a VFR Sectional with a series of blue lines. Within these blue lines, the floor and the ceiling of the Class B airspace is defined. The lateral boundaries of Class B airspace are individually tailored to facilitate arriving and departing traffic operating under IFR. Class B airspace extends from the surface to generally 10,000 feet (3,000 m) MSL. In Denver, Colorado and Salt Lake City, Utah, the ceiling is at 12,000 feet (4,000 m) MSL, while in Phoenix, Arizona, the ceiling is at 9,000 feet (3,000 m) MSL.  It is important to always consult your chart for the most current floor and ceiling information. Aircraft must establish two-way radio communication with ATC and obtain a clearance to enter Class B airspace. All aircraft operating inside or within 30 NM of Class B airspace are required to have a transponder with Mode C. The 30 NM Mode C Veil is denoted on VFR charts by a thin magenta line. VFR traffic must remain clear of clouds and maintain 3 SM of visibility while operating within Class B airspace.

Class C airspace is used around airports with a moderate traffic level.

Class D is used for smaller airports that have a control tower. The U.S. uses a modified version of the ICAO class C and D airspace, where only radio contact with ATC rather than an ATC clearance is required for VFR operations.

Other controlled airspace is designated as Class E, this includes a large part of the lower airspace. Class E airspace exists in many forms. It can serve as a surface-based extension to Class D airspace to accommodate IFR approach/departure procedure areas. Class E airspace can be designated to have a floor of 700′ AGL or 1,200′ AGL, or a customized floor of any other altitude. Class E airspace exists above Class G surface areas from 14,500′ MSL to 18,000 MSL. Federal airways from 1,200 AGL to 18,000 MSL within 4 miles (6 km) of the centerline of the airway is designated Class E airspace. Airspace at any altitude over 60,000′ (the ceiling of Class A airspace) is designated Class E airspace.

The U.S. does not use ICAO Class F.

Class G (uncontrolled) airspace is mostly used for a small layer of airspace near the ground, but there are larger areas of Class G airspace in remote regions.


Next up – Airport and heliport markings and maps!