Angle of Attack Indicator

The Venturay angle of attack indicator serves as a warning when approaching a stall, as well as safest speed on final approach, best climb-out performance, maximum glide range, and to forewarn of dangerous situations such as getting caught behind the power curve. Some pilots say it's the best investment they have ever made. For less than the price of a stall warning, you can get an instrument that gives you more reliable safety information regardless of aircraft weight and conditions. And only the Venturay indicator is fully programmable to your aircraft and automatically adjusts its warnings to reflect your aircraft's current weight.

When U.S. Navy sought a solution to the high rate of accidents in carrier landings, the angle of attack indicator was chosen. Nowadays, angle of attack indicators in fighter aircraft everywhere assist the pilot in establishing the optimal approach angle to their carrier.

For an overview of the different installation options, you can download the installation instructions from the user manual.

We strongly encourage all pilots to consider a stall warning device of some sort regardless of their experience and familiarity with their airplane. It only takes a moment to find oneself in a very precarious situation. And no matter how much flight experience is in a pilot's log book, an angle of attack indicator will significantly reduce the workload while increasing safety - be it during an engine-out emergency or during a standard landing at your local airport. For other suppliers of stall warning devices and angle of attack indicators, please visit our links page.

Stalls

For those of us who learned to fly many years ago, it is a good reminder that a stall can occur at any airspeed. While your POH may stipulate a stall speed, this is under very specific conditions of weight and wing loading (or angle of bank). Not to mention that airspeed indicators are notoriously unreliable under certain critical conditions. Remember: you cannot rely entirely on your irspeed indicator at low speeds, at high angles of attack and during slips – when you need it most!

Although we have been drilled over and over with the lesson that high G-forces increase stall speed, it can be difficult to extrapolate this during flight, especially in emergency situations and unusual attitudes. For example, an aircraft that has a stall speed of 50 knots can stall at 70 knots in a 60 degree bank. Yet, in the same situation, the stall angle of attack remains the same and the Venturay AOA indicator could warn the pilot of the approach to a dangerous angle of attack.

To calculate the stall speed at any given angle of bank, divide the "normal" stall speed by the square root of the cosine of the angle of bank:

Since the relationship is purely mathematical (i.e. irrespective of aircraft type), one can also refer to the following table:

The display is equipped with an internal piezo speaker as well as an external output circuit for connecting to headphones or cockpit speakers.

Approach Speeds

Best approach & landing speed depends on weight. For example, if you are flying a Piper Archer II, your normal approach speed is 66 knots IAS. Now, let’s take an example. It is a beautiful fall day and you are flying alone over the New England forest, admiring the foliage. You have no baggage since it is just a local flight and you land to refuel with 10 gallons of remaining fuel. Your aircraft’s actual weight (assuming the FAA standard pilot weight of 170 lbs.) would be around 1,770 lbs. rather than the POH gross weight of 2550. Of course, you could land at the standard approach speed. But the safer approach could be flown as slow as 56 knots – 10 knots slower!

As we all know, the slower the landing (within the limits contained in the POH and considering stall speed, etc.) the safer the landing. Since energy is proportional to the square of the speed, in the event of an accident, a landing at the higher speed contains 38% more energy to cause damage and injury. In the event of brake failure or a long landing, this could save you from running off the end of the runway.

Yet, many POH do not contain the graphs and information to allow the pilot to even extrapolate this additional safety margin. When they do, you must perform the entire calculation and graphing in advance – no, we would not recommend performing this analysis while on short final. With the Venturay AOA Indicator, all this is done automatically. Simply maintain the approach angle of attack for a higher margin of safety for you, your friends and family, and your aircraft.

Best Glide

Just as with other flight configurations, the POH's Vbg is only an approximation of the speed (at maximum gross weight) that will provide the greatest range. Actually, the charts in most POH provide the the best endurance, not the greatest glide range. Since the optimal angle of glide is a function of weight, we are once again confronted with the need to estimate the factors such as weight and recalculate the best speed – challenging in the best of times, let alone in the event of an engine failure or other in-flight emergency that requires a power-off glide.

Let’s take an example once again. If you are at an altitude of 3000 AGL and your engine suddenly quits, you have to very quickly run through your emergency checklist and try to re-start the engine. The first item on the checklist for most aircraft is: Establish Best Glide Speed. So you push the nose over and trim for a best glide speed of 85 knots IAS for example. According to the POH, your maximum range is 4.2 miles. If you are flying a powerful Cherokee Six at half the gross weight, you will encounter best glide at a speed 30% lower than indicated in the POH for maximum weight. (For those who are curious about the mathematical, the adjustment factor is a function of the square of the weight differential or 85 knots times square-root of 50% = 60 knots). In such a situation, maintaining the higher speed simply forces you into a steeper, faster descent than necessary. (Given that a engine-out glide is typically twice the angle of a normal approach, one should do everything possible to keep this as shallow as possible by maintaining the best angle of attack and airspeed.)

In other words, given the lower lift required for the lower weight, you need to trim for a slower speed to minimize drag . If you maintain the recommended Gross Weight glide speed, you will descend at a much faster rate (over 200 fpm faster), at a steeper angle and you will be unable to glide the distance shown in the POH table. You could reduce your potential landing area by nearly half from 13.8 square miles to a 7 square mile area, in this example.

And since the POH may only show best endurance, what is the setting that will provide you with the greatest range? In such a situation, there is simply not enough time to review and plot your current weight against the POH graph even if it does have such a chart. With the Venturay Angle Of Attack indicator, however, you would simply trim and maintain Best Glide on your indicator.

Those of us who have experienced engine failure – particularly at low altitude or over forested areas – know the value of that extra gliding range and a slower descent that may provide time to troubleshoot, restart the engine, or select a better landing spot. It can mean the difference between an emergency landing and a ruinous crash. For those of us who fly regularly over water, it can mean the difference between landing and ditching.

Best Climb

By now, you have realized that the V-speeds indicated in your POH are very imperfect approximations based on a single weight profile. Since our takeoff weight is constantly varying, we need a more accurate and reliable indicator of the best flight configuration. Once again, the best angle of climb and the best rate of climb are directly related to the angle of attack, regardless of takeoff weight. The Venturay indicator provides both critical angles on its panel.

Power Curve

Many instructors warn against getting caught on the “backside of the power curve” without properly explaining the significance of it. And, although this is one of the most fundamental concepts of flight aerodynamics, there is no instrument that adequately warns the pilot when the aircraft is on the dangerous side of the curve.

Simply put, the power curve is a line representing the drag of an airframe at a given engine thrust. While you can shift the position of this curve up or down, its shape does not change. Interestingly, the curve actually resembles the profile of an airfoil with no underside. It is common to visualize the curve in an inverted form, shaped like a stretched “U.” The left side of the curve represents a decrease of drag as airspeed increases whereas the right side represents an increase as airspeed increases. The lowest point on this inverted curve is the “sweet spot” or the point of minimum drag.

The “sweet spot” is usually referred to as Vy – although this speed is only valid at a single specific condition. Better yet is to identify the apex of the curve based on angle of attack. Above this angle, you are “behind the power curve” regardless of weight and the other factors. By using the Venturay AOA, you can instantly judge whether an addition of power will result in an increase in altitude or simply an increase in drag – the latter will occur if you are on the backside of the curve and may result in very serious consequences if you are already low and slow.