Airfoils can be classified as either symmetrical or asymmetrical, based on the camber.
Symmetrical airfoils are called so since their upper and lower surfaces are the same and hence have zero camber. Asymmetrical airfoils have a non-zero camber, meaning their upper and lower surfaces are different.
Traditionally, symmetric airfoils have been widely used, but in the past few decades, aircraft manufacturers have been shifting to asymmetrical airfoils for their better lift and handling capabilities. However, symmetrical airfoils continue to be used till date, especially in aerobatic aircraft.
Shown above is the NACA0012, a popular symmetrical airfoil. It was used in the rotor of the Bell 205 UH-1 helicopter.
Shown above is the NACA4412, another popular asymmetrical airfoil. It was used as the outboard wing airfoil in a variety of aircraft including the Avtech Jabiru and the Aeronca 65- TAC Defender.
To further understand airfoils and their working, airfoil terminology needs to be grasped. The following terms are typically used while describing an airfoil.
- Leading Edge – The foremost edge or tip of the airfoil profile which comes into contact with the air first.
- Trailing Edge – The rearmost point of the airfoil profile. It serves as a converging point for air diverged by the leading edge.
- Chord – This is the shortest path between the leading and trailing edges. The line formed is called the Chord line.
- Mean Camber Line – Line joining the leading and trailing edges equidistant from both lower and upper surface.
- Maximum Camber – Maximum distance between the mean camber line and the chord line.
- Maximum Thickness – Maximum thickness of the airfoil, measured by the distance between the upper and lower surface.
- Camber – Camber can be defined as the asymmetry between the upper and lower surfaces. It is usually expressed as a percentage called camber percent chord.
- Angle of attack – It is the angle of inclination of the airfoil relative to wind.
Airfoils can be optimized for different performance criteria.
The rotor of the S97 Raider, wing of the SR71 Blackbird, empennage of the B787 or even a dolphin’s flipper all function on the same base principle however their airfoil profiles vary greatly.
Airfoils (also called aerofoil) can be defined as the cross-sectional profile of a wing, propeller rotor or turbine. It’s a streamlined shape designed to provide lift. The principle behind how an airfoil generates lift is simple – the lower part of the airfoil has high pressure while the upper part has low pressure. Air flows from the high pressure region to low pressure regions, thereby producing lift, as shown in the figure below.
In the figure above, a CFD (Computational Fluid Dynamics) result of a rotor blade featuring the NACA23012 airfoil, performed on Ansys is shown. We can see from the result that the air below the airfoil has higher pressure than air above it and that is how the airfoil generates lift.
Controlling a flash flight on Infinite Flight is perhaps the most difficult challenge for a controller. Here are some tips for how to be successful and not get overwhelmed.
Throughout this post, I will use the flash flight I controlled as approach (CYVR-KSFO) as an example.
Plan, plan, plan
Planning is the most important part of controlling a flash flight. First, do not control a flash flight if you don’t have experience controlling hubs. Just don’t do it – your service will be poor and your DMs will be flooded with messages when you close. Otherwise, the best way to plan is by:
- Checking out the ground layout by going in solo and taxiing around to find points of conflict, runway crossings, etc
- Spawning on the IFATC server and looking at the procedure(s) in use
Another important step of planning is to coordinate with other controllers. In our IFATC Discord, I posted the below picture and message to show the Center controller what would be the easiest and most expeditious plan for approach and the pilots. Since everyone was coming on the STINS3 STAR for this flash flight, they could be split onto the two downwinds and vectored to intercept from there.
Additionally, frequencies must be split with the amount of traffic a flash flight generates in order to give the pilots a good service. Do not try to take both tower and ground or approach by yourself – other controllers want to help! For this FF, we split approach by runway.
Execute and Adjust
Now, you’re all set, right? Not quite! Executing is easy enough if you’ve planned well, but what happens when 4 planes come blasting in from LAX? This is where communication comes in. You must communicate with the others who are controlling the airport. In my scenario, I asked center to give approach controller who was servicing the other runway the next ~5 flash flight planes while I handled those coming from LAX. It went flawlessly and we returned to the original plan afterwards.
Take screenshots of your immaculate work
This is a prime opportunity to post all the plane trails, enjoy!
Credit to @JayIOM (tower), @alberto_lopez (28R approach), and @PlaneGeek (center) for their amazing help during this flash flight!
Version 21.2.0 of the ATC Manual is now live here. The following changes are effective on June 9, 2021.
1A.5.2 – Removal of minimum activity % for radar training
Radar Training Requirements:
– Minimum of 60 days at the rank of Specialist
– Minimum of 2000 all-time operations
– Attend a minimum of 10 training sessions per 30 days
– [NEW] Maintain an active controlling record *over the previous 30 days to ensure
proficiency (this will be determined by the Recruiter at the time of application)
*An active controlling record is considered to be 2-3 ATC sessions per week.
6.10.7 – Pro Tip added to specify reduced separation application for parallel ILS
7.5.8 – Minor change to radar training flow chart
The region assignment program allows for new controllers to select one of ten global regions around the world, control any airport within that regional boundary at any time, and remain within their area of operation on a more permanent basis. Read more about the change here.
Awesome work from the following 20 controllers for being the most active out of our entire team in the past 90 days.
If you are interested in becoming an IFATC controller submit an application to get started!
After a successful internal launch of our new Discord server, we are now opening it to the public!
Join on our Discord server
We previously were using it for internal team discussion but now you can join and get a behind the scenes look at what goes on in our group.
We have a bunch of channels set up for you to chat and have fun with other readers and our team. You can share any ideas you have for posts, AMAs, or anything to improve the group.
Then there’s read-only channels for non-team members to view our writing activity, analytics, contributor post submissions, videos and announcements.
If you are an IFATC member you can apply to become a writer for our group right in our server.
As iron sharpens iron, so one person sharpens another. – Proverbs 27:17
When iron blades are rubbed together, each becomes sharper and thus more effective.
People should be questioning, encouraging, coaching, and challenging each other to better each other.
Controlling is a constant feedback loop and we should not be worried about receiving or sharing feedback.
A trend has been noted for the use of radar vectors as a substitute for a missed approach when an aircraft fails to intercept the localizer for their [ILS approach](https://infiniteflight.com/guide/atc-manual/6.-radar/6.10-instrument-landing-system-(ils). This reinforces poor piloting and cuts corners on the service we provide! If an aircraft fails to intercept they should be issued a new vector back across final or a missed approach to try again. In busy scenarios or following repeat errors controllers may issue a warning or utilize the
Failure to complete instrument approach Violation.
Another alternative (if weather supports it) is to quickly advise them to expect the visual, report in sight, and clear. This is the preferred alternative so they have an assigned runway with positive control from ATC.