About Us

Who We Are

PY Aviation is a Service Disabled Veteran Owned Small Buisiness with over 30 years of aviation experience providing Air Traffic Control, TERPS, Part 77, Consulting and Application development for Obstruction evaluations.

Our Services

We develop MAST (Mobile Aerodrome Safeguarding Toolkit) which evaluate airport imaginary surfaces and TERPs surfaces for the effect they may have on an airport.

We Value Our Customers

Our customers and the pursuit of Aviation Safety drives us to look at every angle and provide the best solution at a cost effective price. 




SlopeVIEW is an Augmented Reality application that allows for a quick assessment of Approach, Departure and Transition surfaces to see if penetrations exist.



MAST is an Application that generates FAR Part 77, Annex 14, DoD UFC, FAA Airports GIS and Airport Design Surfaces and ingest obstacles to completes an evaluation is seconds.  MAST is mobile so you can have it on the Airport with you. 

Daily Airfield Inspection


Still working with with excel spreadsheets or printed forms to complete your Airfield Inspections.  DAIC is an application that automates this process and captures any issues or special events during the day.  Allows for the creation of workorders.

Conduct Online FAR Part 77 Evaluation

FAR Part 77

FAR Part 77 or Annex 14

The data entry screen for the Online FAR Part 77 Evaluation Tool

Allows for single evaluations. Select this link to run a sample evaluation . Contact us if you wish to run a large number of evaluations. We evaluated over 30,000 obstacles one time for a customer.

How We Evaluate


Using the 28 Day NASR data we evaluate the point/s to determine if they fall within any of the FAR Part 77 Imaginary Surfaces.  Then display the results in a CSV or HTML output.

What Do We Evaluate


We evaluate the US Civilian and DoD surfaces contained within JO 7400.2.

Pricing For Evaluations


 Our pricing plan depends on how many evaluations you purchase.  The more you purchase the lower each evaluation cost.  Evaluations as low as $25 exist.

TERPS Evaluations


Once you have conducted a FAR Part 77 evaluation and a Penetration exists, the user will be given the opportunity to complete an online TERPS evaluation.

Though your object penetrates FAR Part 77 does not mean it effects the Instrument Approach or Departures at your airport and a favorable determination may be possible.


Check out this short video on how easy it is to use SlopeVIEW to evaluate obstruction penetrations around you airport.


Mast In Action

MAST White Paper

MAST Airport Surface Obstacle Evaluation


MAST can be used to evaluate obstacle elevations against surfaces defined in various FAA standards such as Part 77 and AC 150/5300-18B, DoD UFC standards along with the ICAO Annex 14 standard. It can be applied to airports anywhere in the world for existing or proposed obstacles or runways. MAST also provides the ability to create custom surfaces. 


The inputs to the MAST program are commonly available airport and runway data such as airport elevation, runway ends and elevations along with obstacle data. MAST can also import runway profile survey data points along the path of the runway. Airport data can be created manually within the program, imported from a tab delimited CSV file, or from the NFDC APT.txt file that is available from the FAA NFDC web portal. Obstacles can be created manually within the program, imported from a tab delimited CSV file or from the DOF.dat file that is available from the FAA NACO web portal, the URL of which is built into the MAST program for easy access.


The evaluation process involves loading one or more airports and their runways, choosing the surface types to be evaluated, e.g. FAR Part 77, selecting the runways that are to be evaluated, loading the obstacle sets to be evaluated, creating user defined obstacles as necessary, then running the evaluation. MAST will depict the surfaces and the evaluation results. Obstacles in blue were not evaluated because they were not in any of the surfaces. Obstacle in green were evaluated and found to be not penetrating any surfaces. Obstacles in red were evaluated and found to penetrate one or more surfaces.

The surface definitions of the various standards are installed within the program. Custom surfaces can also be created within the program. The surfaces are generated dynamically during each evaluation using the airport data and the surface definitions. WGS84 calculations are used to generate the surfaces similar to those of the obstacle evaluation process. Once the surfaces are generated the obstacle evaluation engine is used to examine each obstacle that is loaded in the program map view. The evaluation engine determines if an obstacle is within a given surface and performs the appropriate distance and slope calculations.


The MAST program generates evaluation results data for each obstacle and for each surface in which the obstacle is located. This data can be viewed by obstacle within the obstacle definition or all the results can be viewed in a separate table within the program. The evaluation results can be exported to a tab delimited CSV file. The surfaces and the evaluated obstacles can be exported to Google Earth.



MAST uses WGS84 calculations that have been validated against sample data found in FAA order 8260.58A. Its calculations have also been successfully compared against three other WGS84 calculators. The program has been tested extensively using various airports and runways. 

Evaluation Example

The following example evaluation provides a brief overview of the evaluation process. Details for loading and preparing the data can be found in the program documentation.

Load the KLFI airport from the NFDC APT.txt file. Load the DOF obstacles for KLFI. Edit RWY 26 and set it to Part 77 PIR and include the Specially Prepared Hard Surface option.


Create the two manual obstacles below:
1. Name: boat, Latitude: 37.088603973, Longitude: -76.338241577, MSL Ft: 60, AGL Ft: 60
2. Name: boat, Latitude: 37.087455679, Longitude: -76.335963467, MSL Ft: 234, AGL Ft: 234
Runway information:

1. RWY 08: Latitude: 37.077644, Longitude: -76.376429, Elev: 7.3 MSL Ft

2. RWY 26: Latitude: 37.088118, Longitude: -76.344653, Elev: 6.4 MSL Ft


Obstacle 1 is in the approach surface and Obstacle 2 is located in the approach transition surface. Obstacle 1 should be evaluated against the approach surface elevation at the perpendicular intercept of the runway extended centerline and the obstacle. Various WGS84 calculations were performed to determine that the distance along the centerline at the perpendicular intercept point is 1596.96 ft. Applying a slope of 50:1 and adding the starting elevation yields an evaluation elevation of 38.34 ft. The obstacle is 60 ft. so there is a penetration of 21.66 ft. The obstacle information dialog shows the evaluation of two surfaces. Item 1, the horizontal surface, shows a clearance of 98 ft. Item 2, the approach surface, shows a penetration of 21.48 ft.
Obstacle 2 shows both the distance along the centerline, 2052.58 ft Y distance, and within the transition surface, 379.05 ft X distance. The Y slope of 50:1 and the X slope of 7:1 are applied to yield an evaluation altitude of 101.60. The evaluation results are show in the right image below.

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PY Aviation, LLC