Tuesday, June 18, 2019

A SPIN IS A SPIN

On 23rd May CASA released a Safety update : spin recovery training which “highlighted that there can be varying interpretations of an ‘incipient spin’, and this has led to aircraft not approved for intentional spins being used for incipient spin training and assessment.”
Issue 2 of CASA’s Flight Instructor Manual of December 2006 has a Chapter on Stalling which includes the technique for stall recovery “when the wing drops”. There is also a Chapter on Spins and Spirals which includes two different techniques for recovery from an incipient spin. On page 52 it explains the situation where the spin is entered in the normal manner and recovering “before the spin develops fully”. On page 53 it describes the same entry technique however it goes on to state “as soon as the aeroplane has stalled and commenced to yaw take the appropriate recovery action.” That recovery action is different than on the previous page and is identical to that explained in the earlier chapter for a stall with a wing drop.
Incipient spins and training requirements
The Safety update states “CASA is developing further guidance material in relation to the conduct of incipient spins and advanced stalls and how to meet the flight training and testing standards in the Part 61 manual of standards. We expect to finalise these over the coming weeks.”
I note that the Flight Instructor Manual is not listed on the Manuals and Handbooks page of the CASA website although it is still available on the website so I am not sure of its status as current guidance.
That Safety update further stated: “The conduct of an incipient spin in an aeroplane that is not approved for spinning places the aeroplane outside the normal operating envelope into the safety margins provided by the aeroplane certification standards for airframe structural integrity and demonstrated ability to recover from the manoeuvre.”
To me that is a very clear interpretation of the limitation of an aeroplane type which is not approved for intentional spins. i.e. an incipient spin is a spin and if a type is not approved for intentional spins then conduct of an incipient spin is not permitted.
CASA’s definition of aerobatics is also relevant in this situation.
DEFINITION OF A SPIN
It is important to note that CASA also stated that “Flight training operators, their Heads of Operations and Flight Examiners are obliged to ensure that aircraft used for training, flight reviews and testing purposes are certified for the manoeuvres being performed.”
The USA FAA’s Advisory Circular 23-8C, the FAR 23 Flight Test Guide, describes a spin quite generally:
“A spin is a sustained autorotation at angles-of-attack above stall.”
It goes on to describe other attributes of a spin and explains when a fully developed spin has been attained. It does not mention an incipient spin at all.
There are other descriptions of incipient spins, fully developed spins and spins in general around that pilots may be more familiar with however there is no single definition which is broadly accepted. I am going to use that one in AC 23-8C because that is the one used by flight test pilots and engineers. It is particularly important because they are the people who determine whether a type is approved for intentional spins or not and they write the words in the approved Airplane Flight Manual or Pilot Operating Handbook. After all, AC 23-8C explains how information is to be presented in an AFM or POH.
i.e. I would expect the word “spin” in the aircraft manual to be consistent with that description of a spin in the FAR 23 Flight Test Guide. It is a simple description of a spin so it is not too hard for a pilot to determine whether the “incipient spin” manoeuvre being performed is a spin or not.
SPIN CERTIFICATION IN NORMAL CATEGORY TYPES
Let’s look at another relevant document from the USA in relation to a small aeroplane type certified in normal category.
The FAA’s AC 61-67C, Stall and Spin Awareness Training, explains the background to spin test requirements of normal category types: “Normal category airplanes are not approved for the performance of acrobatic maneuvers, including spins, and are placarded against intentional spins. However, to provide a margin of safety when recovery from a stall is delayed, normal category airplanes are tested during certification and must be able to recover from a one turn spin or a 3-second spin, whichever takes longer, in not more than one additional turn with the controls used in the manner normally used for recovery or demonstrate the airplane’s resistance to spins.”
So, normal category aeroplanes are only intended to perform stalls. You may know that the type you fly has been tested for recovery from a one turn spin however that does not mean that you are permitted to intentionally enter a spin and recover before one turn! To emphasise that, the AC goes on to state: “For normal category airplanes, there must be a placard in front of and in clear view of the pilot stating: “No acrobatic maneuvers, including spins, approved.” We now know that the relevant definition of a spin is simply a stalled autorotation which is sustained. It then states:
“The pilot of an airplane placarded against intentional spins should assume that the airplane may become uncontrollable in a spin.”
UPSET PREVENTION AND RECOVERY TRAINING
In 2016 the FAA rewrote their Airplane Flying Handbook and Chapter 4, Slow Flight Stalls and Spins, became Maintaining Aircraft Control: Upset Prevention and Recovery Training. Its explanation of the incipient spin did not change and it still states: “The pilot should initiate incipient spin recovery procedures prior to completing 360° of rotation. The pilot should apply full rudder opposite the direction of rotation. The turn indicator shows a deflection in the direction of rotation if disoriented.
Incipient spins that are not allowed to develop into a steady-state spin are the most commonly used maneuver in initial spin training and recovery techniques.”
The Airplane Flying Handbook has an excellent description of their Stall Recovery Template which is somewhat different than the explanation in CASA’s Flight Instructor Manual. Interestingly, the stall recovery procedure in the new Airplane Flying Handbook has changed from the previous version and now seems consistent with the FAR 23 Flight Test Guide.
The Airplane Flying Handbook goes on to explain their Spin Recovery Template which prompts one further thought. If you intentionally put the aircraft into a situation where the spin recovery procedure (per the AFM or POH) is subsequently required for recovery then you have intentionally entered a spin. Only do that in a type approved for intentional spins within the allowable weight and CG envelope.

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