Flying in Thermals - Thermal Etiquette & Protocols

Nick and Christophe FAPS aerodrome thermal

Thermal Etiquette :

Introduction:

As a novice to flying in Thermals (ie “thermalling”) - principal concerns / considerations is well justified.

        

     Touring Motor Glider Pilots – inevitably will find themselves in the same airspace with other users, such as power aircraft, etc – and unless you are in a dedicated TMG space (or pvt airfield, etc) – the principal is - you will naturally follow basic standard procedures.

The question is – what happens in thermals? What do I do amongst other TMG / “gliders”? The same principal as above applies. In essence – do what “they” do. Therefore understand what / why they do – when they do it!

Glider pilots (due to the nature of their flying, especially in competitions) is not separation paranoid. Though when observing an un-known TMG in or near a haggle - you will see them taking a cautious approach – since they do not know your competency – and immediately will assume that your are – “some power pilot”!. (Do not take exception if “gliders” would suddenly just break-off and seemingly run off to the next thermal / cloud base / ridge, etc).

·         On the other hand power orientated pilots - get nervous when there is traffic 10 miles around, thus avoid sounding like an ATC. (Though good lookout and good reporting is commendable).

·         As soon as the other thermal occupants realize you are – intentionally in the thermal – and committed to flying it – they will accept your presence.

·         Remember “gliders” have the right of way – and you have the privilege of an engine. (So if necessary – declare yourself a glider / engine off – and follow glider procedures).    

Airmanship Notes - for TMG pilots in thermals:

ENGINE OFF - Do not be pressured to fly engine-off, when thermalling - doing PAS (Power Assisted Soaring) is fine – your propeller poses no threat to any other user.

LOOK OUT – gliders tend to fly in the lift band under clouds – their favourite place / altitude - within 500vt of could base (if not 50vt under /in cloud base).

RADIO PROCEDURE – it is ONLY courtesy to call the nearest glider in the thermal – as you approach: (a) your call sign, (b) “his call sign (see usually – 2 digit tail sign), … “Joining thermal” – from which direction, indicate above / below him.”. Similarly if you move on to the nest thermal / cloud base – example: (a) your call sign… “leaving thermal” – to the ? (direction) your call sign” 

·         (Do not be surprised if in any event there is no reply – on any standard frequency, nor – the Official SA Glider frequency 123.40 / (45). Glider pilots in practice – frequently fly the entire flight (which could be hours overhead the airfield at grat altitude of distances of 1200 km) - on the frequency of airfield of origin, or - some obscure “personal/team frequency”).   

NO ASSUMPTIONS – do NOT assume that because - he / she is:

·         is in a glider (at 16 000 vt) that they are experienced / competent (it could be a student with 6 hours or less total flying time / on a solo flight) –

·         because the glider is in a tight turn – it is not necessarily in a thermal / lift 

·         on the lookout -  that they know you are there! ( or see you - in approach to, or leaving the thermal ...).

GO with the FLO – do not make any sudden / adverse manoeuvres:

TMG on average is more agile in manoeuvring than the average glider. The 15m gliders, or aerobatic versions have exceptionally good manoeuvring ability, but the 18 to even - 30 meter wings, fully loaded with water ballast, etc – have slow roll rates, wide shallow turn and bank angles (preserving lift).

GOLDEN SURVIVAL RULE: Avoid – “double blinds spot” positions.

Blind-side flying: SHOULD NOT happen in any event. Gliders/ TMG BLIND SPOTS are –

(a) directly angled back (most gliders looking back, can not see the rudder, exceptions – ex: Libelle);

(b) directly angled forward down (most gliders looking forward does not have a 45 + dg down – except ex Speed Astir, with glass to the tip of the nose).

Thermal Protocol:

The standard protocol / (competition regulations) –  within the Aerodrome airspace (designated altitude / reasonable 5 NM / 8 km)  – or below 1500vt AGL,  thermal left /anti-clock wise.

(1)  The aircraft craft already in the thermal (considered to be above you) has right of way;

a.    Therefore: Enter the thermal – either (just) below or (well) above the glider already in the thermal.

(2)  Enter the thermal turning the same direction as the nearest aircraft above higher  you – already in the thermal;

a.    (NOT the other aircraft above – or below him).

(3)  GOLDEN THERMAL RULE: Position yourself opposite the other plane!

a.    Especially if it is vertically higher than you – and even if it is substantially higher above than you.

b.    If you are on top (or the enter the thermal (well) higher  – he will / should be (re-) positioning according to your - direction (diameter of turn, speed, etc).

In practice: 

(i)       The answer / basic question is - Speed control!!! Remember you are not going up because you are essentially flying faster than he in the circle at an incline (like in a power plane). Actually - despite turning in a circle – relative to each other - you are going up straight.

(ii)     If you maintain your opposite position – and assuming that you are climbing faster, you will simply eventually move in next / opposite him, for a turn or two – and then higher (and then you’re in charge!). This is a very rewarding feeling – perhaps some of the ultimate flying experiences – and unique to the soaring environment.

(iii)   It can be very close (opposite position) in summer – relatively wide in winter, due to thermal diameter and strength

Thermal Competency Requirements (Thermal C R):

Exercise 25: Engine shut-down & restarting the in flight

Aim: Most engines - especially two-strokes, will at some time or another stop whilst in flight. It is important that the learner does not panic but is prepared mentally for and able to cope with the situation.

·         In TMG engines are deliberately turned-off in flight for soaring and landing purposes. It is important that the learner understands the procedures and safe operations parameters.

Exercise 28: PAS (Power Assisted Soaring) techniques

Aim: To develop the ability to: “The continuous in-flight practice of the conscientious exploration of the total (potential, latent, etc) energy index of the aircraft - to cover the greatest land distance in the shortest space of time with the least amount of - “total” energy (including fuel) consumption” - in a Touring Motor Glider.

Exercise 29:  Soaring techniques 

Aim: To – safely and efficiently operate the Touring Motor Glider – as a “sailplane”, engine off configuration, for flight times exceeding 0H30M –  inclusive of soaring (ascending gaining 50% on the safe shutdown AGL height). 

Exercise 33: Loose Formation / Group flying

Aim: To safely fly in loose formation with other aircraft - and know safe landing and taking off procedures – in congestion.  

Notes / advice:

 Close loose / incidental formation & thermal flying.

Roelofse - PRINCIPAL SAFETY RULE: See the head / face (of the other pilot).

This is confirmation that you are not - (A) in a blind spot, and –

 (B) depending on circumstance it conforms / insures –

·         the basic “2 sense rule / double check”  in all glider operations – confirmation on any situation / instruction is: Visual & Audio. 

(i) Accidents / Incidence RARELY happens when ONE of the TWO pilots – or observers, can see each another – (it also helps if you know there is another glider – even if you can’t see it (Speak-up, Glider pilots are notorious for non-communication!).

(ii) Trouble starts – when both aircraft is in each other blinds spots – compounding the trouble is the believe that the other guy is seeing you – and will take evasive action (whilst he is thinking the same).

(iii) Do not sneak-up on another glider / TMG (at least his operating space – example when on a run – ask the question: How high can he pull up, in a dolphin, (at this speed), turn out, etc? If you have to have a closer – final run, thermal, etc announce it. You might just be surprised to find there is one or more stalking you!).

Roelofse Notes: There are good reason for concern – such as in a competition thermal haggles, especially at the first thermal, the going up part is still OK. The chaos starts - when all of these gliders, perhaps 30 plus sometimes, level off under one very small cloud (base). In competitions and out-flights gliders tend to stay close in small groups (like a long distance road marathon) – and final glide show their real capacity, one would still even see 2 - 3 gliders within seconds from each other.) Fortunately you do not have to haggle at cloud base, fly on - and PASASA sanctioned events / competitions are structured to avoid the first “collective haggle”. 

Roelofse strongly advocates: The “left hand” / “anticlockwise” thermal protocol – (and believes / advocates it should be regulated). “It is only a sensible solution to an otherwise chaotic scene – especially from a safety point of view, ... there is really no alternative”. ….” If other procedures / basic / principals can be enforced in the aerodrome space – such as standard left hand circuit procedures then all the more these extended activities which is nothing more than aircraft, after take-off, in climb-out phases”. …” Remember most TMG is also side –by-side – and left hand pilot positions … There are various diverse objective reasons in support of such a standard operating procedure – ranging from the Carioles effect, to default left-hand circuits, left hand orbits in controlled airspace, most TMG pilots (other traffic) left hand seat (easy look-out; to the not so-common common sense”.      

Basic Thermal Techniques

Roelofse states: …“effective thermalling- is not flying in a circle”, as one (power flying) would usually do an orbit. He makes valid arguments and states that: “Good thermalling involves the acute ability to role and yaw in the turn according to the thermal pathology without actually changing attitude / relative angle of attack (ie pitch – and/or if so required, then to do so – to obtain an optimal ideally balanced plane)”.

TMG’s in general are not as twitchy (as oppose to LSA with high wing loading), especially if you have a clear understanding of the rudder. (Ailerons should not pick up wings. Rudders keep wings straight and level). Though the large wing areas usually provide ample excitement when approaching a thermal, all you need to do is to ride it (dolphin).

Initial thermal phase - Unlike in power planes where you veer between thermals – here you actually deliberately feel your way into the thermal. The wing that lifts, gives indication - to slight direction change, usually with rudder input (keeping wings level), as the lift build / increase,  you pull back on the stick – determined by the thermal strength (and aircraft flight envelope), sometimes past stall speeds. As the lift weakens – nose down recovery and re-direction action is taken – for coarse / heading to continue the cross-country route. This technique – is also referred to as “dolphining ”  (in reference to Sea dolphins motions).  

·         Instruments lag on average 3 seconds – hence you need to acquire an almost intuitive anticipation for identifying or recognizing lift.

·         Special awareness should be tuned to – engine restart height, out landing space, wind directions, cloud formations, etc.

·         Never fly through “bad air” / sink twice!   

Thermalling is not flying in a circle / hold. It starts off (as the initial phase of a dolphin move), moving into the thermal, but then – as you find your way into stronger lift – you would typically pull up high (climbing turn towards the perceived thermal center), sharp and pronounced, near stall (actually the  minimum required inertia), while turning in towards the core and bank at least 45 degrees. The actions can be quite dramatic, almost violent as you reduce speed in the upward climb, to gain attitude, maintaining a tight turn not to pass the outside thermal boundary. Recover and maintain speed, at the bank angle, in the prevailing conditions.

·         There are various techniques in the turn – such as to have the yaw string off to the outside, which in effect means you are side slipping into the thermal, it is also a good spin avoidance technique.

Thermal boundaries can well defined, sometimes a virtual sharp edge – if you miss it and slip into the sink in this unusual “high bank turn” attitude – as it all falls away under you suddenly without warning, - it makes for a good wake-up call. ‘Fokus”! Student pilots usually scare a bit and tend to level off and get their wits about them first, before turning in for the next attempt. With experience – simply pitch nose up a bit, slight less bank, pull back into it.

Usually in cross county - Flying 3 to 5 turns, (gaining 500 to 1500 ft in reasonable lift) and then apply the common exit technique. If there is no rush / time limit – simply climb it to the top.

·         Pay careful attention to spatial / situational awareness, you might be climbing at a reasonable rate – but you could also be drifting with the thermal over / into dangerous terrain. Similarly the top of decent can be the base of a major Cumulus Nimbus (CB) cloud – which could be the source of great lift – until it over develops (“anvil”) and the source of heavy rain, micro burst, heal, lightning strikes. 

Common Thermal exit technique: Simply level out – from the thermal position - straight and level onto coarse / heading. Pitch the aircraft nose down, increase to flying speed - and “run”. Increase the speed through the follow-on sink, - onto the next thermal (see reference to ideal speed / & RPM, etc).

·         Also see: “advanced thermal exit technique

Irrespective of how intense the thermalling – always come out exactly on target / track despite the fact that you pay little or no attention to the compass or GPS. (Spatial and Situational Awareness – is one of many flying traits glider pilots develop, in addition to Power Pilots usual situational awareness). Flying outside the cockpit, an acute understanding of the difference between spatial and situational awareness, is essential.

·         Instead of looking straight ahead on the horizon (like power pilots) – a good technique is looking out at 45 degrees to the horison (roughly between to the horizon / aircraft nose – and the wing) – in the direction of the turn, to size up the wing tip and nose in relation to the horizon. (As appose to just looking over the dashboard to the horizon (managing pitch), having only one dimension, etc.)

·         There is no time for turn-slip indicators. The most valuable tool in thermalling is a “yaw string” (affectionately known as a “wolletjie” / (wool string) in South Africa). 

Advanced Thermal Techniques

The key is – dominating / “manipulating the thermal” – making it your space (to suit your craft, etc) to your advantage – ie to the disadvantage of your rival - is the primary advanced aim. (Flying for example an old SF 25 - which climbs very good – at low speeds, in a skilled hand - should out-climb  any second and most 3rd generation glass TMG - and even similar pure gliders). He says: “… never thermal from a disposition”.

Dolphin technique – as a cross country flying technique – is well practiced. The basic method of establishing in the core of the thermal is well practiced.  

Being opposite your rival (in “your” thermal) - does NOT necessarily mean the assumed gentleman chivalry position opposite him /her - with the core of the thermal in the “middle” of the two. (When flying a competition – there is little room for … gallantry!) Flying a smaller circle diameter at greater bank angle and lower speed (balancing – additional wing load / to increased rate of ascend), – forcing your opposition wide since they need more speed at less bank to maintain the same lift figures, yet - on the outside the thermal - is weak lift disposition. It means – making them work for their lift. The race is up! The sooner you reach altitude the sooner you can run … It is simple – either you dictate – or you are dictated to.

·         Even under intense the thermal activity – always bear in mind the original  target / track / heading,  despite the fact that you pay little or no attention to the compass or GPS.

o   Spatial and situational Awareness – is one of many acute flying traits required – as “flying outside the cockpit” is vital.

o   During straight and level flight pay attention to horizon markers  and prominent landmarks – for basic direction – and;

o    cloud formations / shades on the ground, for cloud streets / “lift paths”. 

·         The 45 degrees look-out technique - is to focus to the horizon (roughly between to the horizon / aircraft nose – and the wing) – in the direction of the turn, to size up the wing tip and nose in relation to the horizon.

Clouds – as markers for developing / sustained lift. On approach after a stretch / “cross country run” – assess your target position under the cloud according to the combination of the following elements – in order of importance / weight:

·         The “sharp side” (the side where the cloud is rising / is well (distinctively defined with sharp lines)

·         The “sun side” (the side positioned to the sun)

·         The “wind side” (the side from where the general wind direction)

·         The “dark side” / (under section) section (once underneath the cloud – this is primary target areas in search of lift)

Flying your old motor glider SF 25, Fournier, etc (similar to its pure glider counter parts - K6-13’s etc – “clean” is great. But in a turn always fly your yaw string just off to the outside, in these fat wing high lift machines. Roelofse refers to the old trusted technique and advocate it as an advanced “thermal-yaw-technique”. The yaw string indicates slightly outside / opisite the turn direction. It means whereas your inside wing – would usually be flying slower – it is forced it slightly faster – generating more lift. (This is also a good measure against stall, and insipient spin, especially low down). It is the ideal method to keep the turn tight, less wing load (less G force), thus more lift / better rate of ascend, since you can manoeuvre closer to the core of the thermal lift. This yaw attitude can be actively decreased or increased – for example your yaw string is be a bit more pronounced outside, force your glider into a slightly lower bank – more lift, and naturally slower, so you can position yourself closer to the centre of the thermal. 

·         With the yaw-technique – your TMG is slipping into the thermal all the time – instead of rolling out / off the thermal.

Of course – if someone else have you in a yaw-technique centre squeeze and forcing you – into the weaker outer lift area of the thermal … Remember – if you are doing PAS (power assisted soaring) - you can always temporarily adjust RPM / power setting for the 2 or 3 turns it takes to clear the opponent. 

Thus – stick that big fat wing in it. Inevitably it means your rival will have to find away around you – whilst climbing / flying a greater circle (in weaker lift, at higher speed, etc).

Note: Winglets, and certain wing profiles etc - does not take well to the yaw-technique. 

The “advanced thermal exit technique” is defined as a very tight ‘climbing’ turn, through the core whilst climbing (deliberately pulling up) and levelling out on direction / heading, near the stall – as the lift dissipates, put the nose down, increase to flying speed - and “run”. Then simply increase the speed through the follow-on sink, steadily converting the excess altitude into additional speed, (see reference to ideal speed / & RPM, etc).

When truly PAS flying – RPM settings, etc is very important, to achieve the ideal - “total energy efficiency”.  Roelofse states that: In essence the idea is to have an engine setting, that compensates for your TMG sink rate (as to provide a true straight and level), when (as if) flying in continued average identified lift, at a particular altitude / time, etc. (see reference to ideal RPM, etc).

Special awareness should be developed for – safe engine restart height, out landing space, wind directions, cloud formations, lift/cloud streets, etc.

   THERMAL ETIQUETTE – BEST PRACTICE   End Doc Ref PAS  070/1-3

>> The document / extract / summary - is the exclusive property of PASASA / Author: Christophe Roelofse  - and may not be published or distributed in any form of intent without explicit permission fro the author.