Greetings Colorado Glider Pilots! As this year’s thermal soaring season nears, Denver TRACON (radar/approach & departure control) would like to take the opportunity to interact the soaring community via this Letter to Airmen (LTA), and address one subject that is very important for all aviators: collision avoidance; specifically relating to soaring flights within 60 NM of Denver International Airport and other Denver-area satellite airports. 

It is a fundamental principle of flight that those involved in the management of a flight, especially pilots and air traffic controllers, take all necessary action to avoid collision. For pilots, that begins during training by having a knowledge of FAA regulations, including right-of-way rules (specifically 14 CFR § 91.113), and learning/applying those principles during flight. There are, indeed, several levels of type-dependent precedents directing which category/class of aircraft gives-way in a given case. However, the ‘prime-directive’ guiding any PIC is always see and avoid, stated as: “…regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance [is] maintained by each person operating an aircraft so as to see and avoid other aircraft.” 

Advisory Circular (AC) 90-48D “The Pilot’s Role in Collision Avoidance”, is a helpful tool which covers in detail all aspects of the subject, providing information that can help mitigate the potential for collision avoidance, beginning with preflight planning. The AC encourages all pilots to review airspace, NOTAMS, terrain, weather and known/charted aircraft routing, to reduce the chances of midair collisions between commercial and other aircraft. The goal of this letter is to place greater focus on the last of those review categories: known/charted aircraft routing.

Jet aircraft have an especially high-rate of closure speeds vs. other aircraft, and create a special concern, because of limited reaction times for see and avoid. Establishing visual contact from the cockpit is always a challenge, and added speed complicates the difficulty quotient. Thankfully, these fast-movers typically fly along known and/or published routing when transitioning airspace where gliders fly. Situational awareness of established/published/predictable jet routes to and from Denver is step one to avoiding conflict with planes on these routes. The next step is purposely avoiding those areas and routes as you plan and execute your soaring flight; keeping in mind that these routes are like aerial ‘super highways.’ 

You may question why ATC does not just ‘handle’ these potential conflicts. In fact, ATC works continually to reduce or eliminate probability of unexpected conflicts between powered and soaring aircraft who are in contact with them. Unfortunately, some factors complicate this, such as, limited numbers of transponder equipage in gliders, and greatly variable glider flight paths and/or altitudes as pilots seek lift. The bottom line is many gliders remain invisible to ATC, and to other pilots/aircraft with equipment capable of displaying traffic. 

Denver TRACON reached out to local glider experts that operate in our airspace, including glider designated pilot examiners. During these conversations, we learned that glider pilots do not always have reference material available, which depicts Standard Terminal Arrival Routes (STARs) or Standard Instrument Departures (SIDs). These are the primary routes that you can be certain have heavy jet arrival/departure traffic. The experts explained that some pilots do not have access to appropriate charts, or chart-inclusive apps on ‘electronic flight bag’ tools such as an iPad with planning software and moving map/traffic displayed (e.g. Foreflight, Garmin Pilot, etc.), especially in the smaller glider cockpits. 

So, what can a glider pilot do to better prepare during preflight to avoid midair collisions? Here are some recommendations suggested by the glider experts: 

Preflight planning (see associated images):  

- Obtain a chart that includes STAR/SID information that crosses their operations area. 

- Find SID/STAR routes by looking on the VFR Terminal Area Charts (TAC); and, that chart’s reverse side known as the ‘VFR FLYWAY” chart (examples of both are shown below). Lines of blue ‘arrowheads’ align with these routes. Charts of this type are available in paper, and/or electronically via on-line sources such as skyvector.com.

- Once you understand where the STAR/SID routings are in relation to desired flight & ‘thermal’ areas, plan your flight to remain clear of those ‘super-highways’ before you depart. 

In-flight: 

- Utilize correct scanning and other techniques as suggested in AC 90-48D

       www.faa.gov/documentLibrary/media/Advisory_Circular/AC_90-48D_CHG_1.pdf

 Near Midair Glider/Jet Occurrence Example (see associated image):

Pilot awareness of your planned/current/projected glider flight-track, in relation to SIDs and STARs, or other identified high traffic-density areas, is critical. The glider flight-track shown in the image below depicts an actual example of a glider flight west of Boulder (KBDU). The part of the glider route in the red oval includes a significant amount of time circle-climbing and/or straight-line flying, on a westbound SID from Denver International Airport. In this case, a ‘NMAC’ (near mid-air collision) occurred between a westbound regional jet, and this eastbound glider.

Area-focused Maps: 

The map excerpts on the following pages focus on the three geo-specific areas of the foothill areas S, W, and NW of Denver, that soaring operations generally occur. ATC routing via RNAV (GPS) standard terminal arrival/departure routes (STARs / SIDs) are shown on each chart. These established routes are not the only routes that aircraft will fly, as ATC will vector other traffic situationally. However, these route locations are predictably populated with turbine aircraft operating at speeds that always include high closure rates with other traffic targets. 

Airports having the greatest number of glider launch activity are shown with blue print and a red circle. Solid lines are arrival routes; dotted lines are departure routes; lines depicted with “x” marks, are vectored routes (typical). Altitudes of route segments are also indicated, where appropriate. 

SOUTHERN Denver Approach/Departure Area Airspace (see image)

WESTERN / Denver Approach/Departure Area Airspace (see image)

NORTHERN / Denver Approach/Departure Area Airspace (see image)

It is our hope that you find the information in this letter to be helpful in the approaching soaring season and those that follow.   If you have comments or questions, feel free to contact the Denver TRACON Airspace and Procedures Office, at 303-342-1510. 

Thank you and safe soaring!