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As I understand it, when jet aircraft were flown from aircraft
carriers, procedures and equipment used with piston aircraft proved inadequate, and the United States adopted a set of devices developed by the British, including the angled deck, the optical glide path, and the angle of attack indicator. By the time the Douglas Skyhawk was built, the angle of attack (AOA) indicator was used with a head up display. Was the head up display used from the beginning, or were there earlier types of AOA indicators with some type of panel display? Were AOA indicators retrofitted to earlier types of aircraft designed without AOA equipment? When did AOA indicators begin to be installed on Air Force planes? Thank you, Peter Wezeman anti-social Darwinist |
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Ed Rasimus wrote:
As I understand it, when jet aircraft were flown from aircraft carriers, procedures and equipment used with piston aircraft proved inadequate, and the United States adopted a set of devices developed by the British, including the angled deck, the optical glide path, and the angle of attack indicator. By the time the Douglas Skyhawk was built, the angle of attack (AOA) indicator was used with a head up display. I think you'll find AOA information available in some format or other all the way back to the early '50s in USAF aircraft. The A-4 had no HUD, at least not until the Marines' A-4M version. There was an Indexer on the glareshield, though. |
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On Jul 26, 11:11*am, "jrw" wrote:
Ed Rasimus wrote: As I understand it, when jet aircraft were flown from aircraft carriers, procedures and equipment used with piston aircraft proved inadequate, and the United States adopted a set of devices developed by the British, including the angled deck, the optical glide path, and the angle of attack indicator. By the time the Douglas Skyhawk was built, the angle of attack (AOA) indicator was used with a head up display. I think you'll find AOA information available in some format or other all the way back to the early '50s in USAF aircraft. The A-4 had no HUD, at least not until the Marines' A-4M version. There was an Indexer on the glareshield, though. I misread the picture of the display system on the A-4. I see now that the three color display is at the lower edge of the windscreen where it can be seen in the pilots peripheral vision. In another source, I found that British AOA systems circa 1960 for carrier jets had audio output indicating whether AOA was optimal. Peter Wezeman anti-social Darwinist |
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On Jul 26, 8:29*am, wrote:
As I understand it, when jet aircraft were flown from aircraft carriers, procedures and equipment used with piston aircraft proved inadequate, and the United States adopted a set of devices developed by the British, including the angled deck, the optical glide path, and the angle of attack indicator. By the time the Douglas Skyhawk was built, the angle of attack (AOA) indicator was used with a head up display. Was the head up display used from the beginning, or were there earlier types of AOA indicators with some type of panel display? Were AOA indicators retrofitted to earlier types of aircraft designed without AOA equipment? When did AOA indicators begin to be installed on Air Force planes? Thank you, Peter Wezeman anti-social Darwinist There are two types of sensor, a simple stall warning switch placed at the stagnation point at whcih stall would occur on the leading edge of the wing and the more sophisticated type that actually gives precise angle of attack. In passenger jet aircraft you will notice usually 4 of these 'vanes' mounted to either side of the cockpit. An A320 has two either side an A380 no less than 4 either side. (Pre FBW these were seperate for pilot an co pilot) In single engine piston aircraft you will see the mounted on the wing tips. In Jets you will usually see similar vertical vanes mounted on the nose to measure side slip. A modern stall warning system uses not only Angle of Attack but side slip to calculate stall warnings since the prescence of side slip effects stall angle, presumably due to the greatee distance the air must flow over the wing during side slip. Some aircraft have an Air Data Probe mounted in the nose which combines AOA, side slip and pitot static (properly called a prandl tube). Usually used for testing due to its precision. Military aircraft have a sort of conical or tube shaped devise with two pressure ports offsest slightly, these have pressure sensors in them that drive a servo motor till they are in balance. This is a 'pressure nulling sensor' I believe the Grumman Cougar gave zero stall warning however an AOA sensor, stick shaker and stick pusher fixed that and gave plenty of warning. I don't see the point giving an aircraft a lot of stall warning as in say a spitfire by given a lot of washout when sensors can now do the job. Reducing aerodynamic efficiency to give a progressive stall development is giving away turning circle and aerodynamic efficiency. Aircraft such as the Ta 152H had such a large degree of washout (3 degrees) they were apparently fully controllable in roll during the stall. Of course you still want good post stall recovery. Slats strike me as a good way to do that. In FBW aircraft the AOA, side slip and prandl sensor data are fed to the ADIRU (air data inertial reference unit) a sort of box of gyroscopes and accelerometers that keeps track of up and smoothes' the jittery aerodynamic data. That Airfrance Flight 547 that crashed in the Atlantic eroute from Brazil to France probably losts its pitot static tube. Normally A330 airbuses have a Honeywell ADIRU with BF Goodrich pitot static tubes but Air France took the optional Thales Units whose pitot tube have a tendancy to not drain water properly and ice up. Apparently the A320 doesn't suffer from this and A330s are getting the A320 sensors Once iced up the FBW system would have detected the inconsistencies and switched the control laws from full to secondary, a sort of semi automatic mode where stall protection and flight envelop protection is reduced. The pilot now has to fly manually. It would have lmited the rudder to stop the pilot from over stressing it accidently. Flying an aircraft whether it be FBW or Normal cabled aircraft without pitot static data at night and the middle of a storm is not easy. |
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On Jul 27, 11:48*pm, wrote:
On Jul 26, 8:29*am, wrote: As I understand it, when jet aircraft were flown from aircraft carriers, procedures and equipment used with piston aircraft proved inadequate, and the United States adopted a set of devices developed by the British, including the angled deck, the optical glide path, and the angle of attack indicator. By the time the Douglas Skyhawk was built, the angle of attack (AOA) indicator was used with a head up display. Was the head up display used from the beginning, or were there earlier types of AOA indicators with some type of panel display? Were AOA indicators retrofitted to earlier types of aircraft designed without AOA equipment? When did AOA indicators begin to be installed on Air Force planes? Thank you, Peter Wezeman anti-social Darwinist There are two types of sensor, a simple stall warning switch placed at the stagnation point at whcih stall would occur on the leading edge of the wing and the more sophisticated type that actually gives precise angle of attack. In passenger jet aircraft you will notice usually 4 of these 'vanes' mounted to either side of the cockpit. *An A320 has two either side an A380 no less than 4 either side. *(Pre FBW these were seperate for pilot an co pilot) In single engine piston aircraft you will see the mounted on the wing tips. In Jets you will usually see similar vertical vanes mounted on the nose to measure side slip. A modern stall warning system uses not only Angle of Attack but side slip to calculate stall warnings since the prescence of side slip effects stall angle, presumably due to the greatee distance the air must flow over the wing during side slip. Thank you very much for your reply. Military fighter and attack planes have angle of attack displays visible to the pilot. Do you see any advantage to having something like this for pilots of airliners, possibly for use as part of normal flying routine, possibly as a back- up and cross check for airspeed information? Some aircraft have an Air Data Probe mounted in the nose which combines AOA, side slip and pitot static (properly called a prandl tube). *Usually used for testing due to its precision. Military aircraft have a sort of conical or tube shaped devise with two pressure ports offsest slightly, these have pressure sensors in them that drive a servo motor till they are in balance. *This is a 'pressure nulling sensor' I believe the Grumman Cougar gave zero stall warning however an AOA sensor, stick shaker and stick pusher fixed that and gave plenty of warning. In FBW aircraft the AOA, side slip and prandl sensor data are fed to the ADIRU (air data inertial reference unit) a sort of box of gyroscopes and accelerometers that keeps track of up and smoothes' the jittery aerodynamic data. That Airfrance Flight 547 that crashed in the Atlantic eroute from Brazil to France probably losts its pitot static tube. Normally A330 airbuses have a Honeywell ADIRU with BF Goodrich pitot static tubes but Air France took the optional Thales Units whose pitot tube have a tendancy to not drain water properly and ice up. Apparently the A320 doesn't suffer from this and A330s are getting the A320 sensors Once iced up the FBW system would have detected the inconsistencies and switched the control laws from full to secondary, a sort of semi automatic mode where stall protection and flight envelop protection is reduced. *The pilot now has to fly manually. I once read that the control sticks on Airbus planes do not have force feedback. If this is still the case, what is the procedure for manually flying the plane without overstressing it? It would have lmited the rudder to stop the pilot from over stressing it accidently. Flying an aircraft whether it be FBW or Normal cabled aircraft without pitot static data at night and the middle of a storm is not easy. Thank you again, Peter Wezeman anti-social Darwinist |
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On Jul 29, 10:25*pm, "JR Weiss" wrote:
wrote: In passenger jet aircraft you will notice usually 4 of these 'vanes' mounted to either side of the cockpit. *An A320 has two either side an A380 no less than 4 either side. *(Pre FBW these were seperate for pilot an co pilot) In Jets you will usually see similar vertical vanes mounted on the nose to measure side slip. A modern stall warning system uses not only Angle of Attack but side slip to calculate stall warnings since the prescence of side slip effects stall angle, presumably due to the greatee distance the air must flow over the wing during side slip. Thank you very much for your reply. Military fighter and attack planes have angle of attack displays visible to the pilot. Do you see any advantage to having something like this for pilots of airliners, possibly for use as part of normal flying routine, possibly as a back- up and cross check for airspeed information? Unfortunately, the "experts" in the Transport Category Airplane world have deemed AOA readouts as superfluous. *Their argument (among others) is that optimum AOA for any particular operation is not constant for a large range of gross weights, so Vref or V2 as defined by the FAA and other regulatory agencies is "better." After 20 years of aircraft carrier operations and 11 years of airline operations I tend to disagree, but I'm not an aerodynamicist... FWIW, the sideslip vanes may be on Airbusses, but they're not on the 747, and I haven't noticed them on any other Boeings. *Harriers had them, and Tomcats had yaw strings (simple and effective). Hi John; I've heard the same thing from the airline industry, and I think they might have a point. I've always wondered how you guys handle the vast differences in gross weights you have when you arrive at the initial approach fix. The Navy as we both know, requires a very stable approach profile so AOA is great for them, as it automatically compensates for the differences in approach weight and the approach is the same AOA regardless of weight. But this assumes a fairly (or at least comparatively anyway) narrow gross weight for the Navy when arriving for the approach on the boat. You guys in the majors deal with what could loosely be described by a Navy fighter pilot as a fair to middling gross weight range on approach. My guess would be that using an optimum AOA on approach might very well not be as viable as using a Vref. I would of course bow to your better judgment on this since you have time in the big boys and I don't. I remember seeing a report from Boeing a while back where they were "discussing" the addition of AOA to the approach equation both with adjusted procedures and panel changes regarding instrumentation. If I remember right, the bottom line on their research was that the front offices and chief pilots of various majors couldn't reach a consensus on the issue strong enough to warrant a major policy change at the top level. There were specific lines who were willing to have their panels equipped with a change from a peripheral AOA indicator to a prominent place on the glass for an AOA tape on the approach mode, but I never followed this through enough to discover were if anywhere everybody went with all this. Dudley |
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Dudley Henriques wrote:
Unfortunately, the "experts" in the Transport Category Airplane world have deemed AOA readouts as superfluous. *Their argument (among others) is that optimum AOA for any particular operation is not constant for a large range of gross weights, so Vref or V2 as defined by the FAA and other regulatory agencies is "better." After 20 years of aircraft carrier operations and 11 years of airline operations I tend to disagree, but I'm not an aerodynamicist... I've heard the same thing from the airline industry, and I think they might have a point. I've always wondered how you guys handle the vast differences in gross weights you have when you arrive at the initial approach fix. The Navy as we both know, requires a very stable approach profile so AOA is great for them, as it automatically compensates for the differences in approach weight and the approach is the same AOA regardless of weight. But this assumes a fairly (or at least comparatively anyway) narrow gross weight for the Navy when arriving for the approach on the boat. You guys in the majors deal with what could loosely be described by a Navy fighter pilot as a fair to middling gross weight range on approach. My guess would be that using an optimum AOA on approach might very well not be as viable as using a Vref. I would of course bow to your better judgment on this since you have time in the big boys and I don't. I remember seeing a report from Boeing a while back where they were "discussing" the addition of AOA to the approach equation both with adjusted procedures and panel changes regarding instrumentation. If I remember right, the bottom line on their research was that the front offices and chief pilots of various majors couldn't reach a consensus on the issue strong enough to warrant a major policy change at the top level. There were specific lines who were willing to have their panels equipped with a change from a peripheral AOA indicator to a prominent place on the glass for an AOA tape on the approach mode, but I never followed this through enough to discover were if anywhere everybody went with all this. I still believe that AOA is a more sensitive indicator of performance than IAS at relatively low airspeeds. That may actually be the "problem" though -- we probably don't want transport pilots pumping the yoke to keep an "optimum" AOA and get the passengers upset... OTOH, the range of handling differences between a "light" (33,000 lb) and "heavy" (36,500) A-6 on the ball and a "light" (170,000 Kg) and "heavy" (302,000 Kg) 747 are quite different (I won't address the A-4, because it wasn't a "heavy" in any sense of the word). The A-6 differed mainly in power response on the G/S, but the 747 differs mainly in the flare. While AOA was critical in the A-6 to keep the hook at the proper angle of dangle to snag the 3-wire, the 747 can be landed comfortably anywhere in the nominal 3000' landing area (first 1/3) of a typical runway. OTOOH, I think a "real" AOA indicator would be VERY helpful in escape maneuvers for WindShear and Terrain warnings. The stick shaker is a useful On/Off switch for backpressure, but a trend indicator via AOA would be much more useful. |
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On Jul 30, 12:03*am, "JR Weiss" wrote:
Dudley Henriques wrote: Unfortunately, the "experts" in the Transport Category Airplane world have deemed AOA readouts as superfluous. *Their argument (among others) is that optimum AOA for any particular operation is not constant for a large range of gross weights, so Vref or V2 as defined by the FAA and other regulatory agencies is "better." After 20 years of aircraft carrier operations and 11 years of airline operations I tend to disagree, but I'm not an aerodynamicist... I've heard the same thing from the airline industry, and I think they might have a point. I've always wondered how you guys handle the vast differences in gross weights you have when you arrive at the initial approach fix. The Navy as we both know, requires a very stable approach profile so AOA is great for them, as it automatically compensates for the differences in approach weight and the approach is the same AOA regardless of weight. But this assumes a fairly (or at least comparatively anyway) narrow gross weight for the Navy when arriving for the approach on the boat. You guys in the majors deal with what could loosely be described by a Navy fighter pilot as a fair to middling gross weight range on approach. My guess would be that using an optimum AOA on approach might very well not be as viable as using a Vref. I would of course bow to your better judgment on this since you have time in the big boys and I don't. I remember seeing a report from Boeing a while back where they were "discussing" the addition of AOA to the approach equation both with adjusted procedures and panel changes regarding instrumentation. If I remember right, the bottom line on their research was that the front offices and chief pilots of various majors couldn't reach a consensus on the issue strong enough to warrant a major policy change at the top level. There were specific lines who were willing to have their panels equipped with a change from a peripheral AOA indicator to a prominent place on the glass for an AOA tape on the approach mode, but I never followed this through enough to discover were if anywhere everybody went with all this. I still believe that AOA is a more sensitive indicator of performance than IAS at relatively low airspeeds. *That may actually be the "problem" though -- we probably don't want transport pilots pumping the yoke to keep an "optimum" AOA and get the passengers upset... OTOH, the range of handling differences between a "light" (33,000 lb) and "heavy" (36,500) A-6 on the ball and a "light" (170,000 Kg) and "heavy" (302,000 Kg) 747 are quite different (I won't address the A-4, because it wasn't a "heavy" in any sense of the word). *The A-6 differed mainly in power response on the G/S, but the 747 differs mainly in the flare. *While AOA was critical in the A-6 to keep the hook at the proper angle of dangle to snag the 3-wire, the 747 can be landed comfortably anywhere in the nominal 3000' landing area (first 1/3) of a typical runway. OTOOH, I think a "real" AOA indicator would be VERY helpful in escape maneuvers for WindShear and Terrain warnings. *The stick shaker is a useful On/Off switch for backpressure, but a trend indicator via AOA would be much more useful. It's an interesting subject and I'm sure in any end analysis, aoa could be integrated into the heavy environment. more than it has been. Personally I like aoa. I've always taught wing and energy management flying from Cubs to high performance singles. The future may very well reveal the benefits of aoa to a wider cross section of the commercial community. Hope so anyway! :-) DH |
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On Jul 29, 9:48 pm, Dudley Henriques wrote:
On Jul 30, 12:03 am, "JR Weiss" wrote: Dudley Henriques wrote: Unfortunately, the "experts" in the Transport Category Airplane world have deemed AOA readouts as superfluous. Their argument (among others) is that optimum AOA for any particular operation is not constant for a large range of gross weights, so Vref or V2 as defined by the FAA and other regulatory agencies is "better." After 20 years of aircraft carrier operations and 11 years of airline operations I tend to disagree, but I'm not an aerodynamicist... I've heard the same thing from the airline industry, and I think they might have a point. I've always wondered how you guys handle the vast differences in gross weights you have when you arrive at the initial approach fix. The Navy as we both know, requires a very stable approach profile so AOA is great for them, as it automatically compensates for the differences in approach weight and the approach is the same AOA regardless of weight. But this assumes a fairly (or at least comparatively anyway) narrow gross weight for the Navy when arriving for the approach on the boat. You guys in the majors deal with what could loosely be described by a Navy fighter pilot as a fair to middling gross weight range on approach. My guess would be that using an optimum AOA on approach might very well not be as viable as using a Vref. I would of course bow to your better judgment on this since you have time in the big boys and I don't. I remember seeing a report from Boeing a while back where they were "discussing" the addition of AOA to the approach equation both with adjusted procedures and panel changes regarding instrumentation. If I remember right, the bottom line on their research was that the front offices and chief pilots of various majors couldn't reach a consensus on the issue strong enough to warrant a major policy change at the top level. There were specific lines who were willing to have their panels equipped with a change from a peripheral AOA indicator to a prominent place on the glass for an AOA tape on the approach mode, but I never followed this through enough to discover were if anywhere everybody went with all this. I still believe that AOA is a more sensitive indicator of performance than IAS at relatively low airspeeds. That may actually be the "problem" though -- we probably don't want transport pilots pumping the yoke to keep an "optimum" AOA and get the passengers upset... OTOH, the range of handling differences between a "light" (33,000 lb) and "heavy" (36,500) A-6 on the ball and a "light" (170,000 Kg) and "heavy" (302,000 Kg) 747 are quite different (I won't address the A-4, because it wasn't a "heavy" in any sense of the word). The A-6 differed mainly in power response on the G/S, but the 747 differs mainly in the flare. While AOA was critical in the A-6 to keep the hook at the proper angle of dangle to snag the 3-wire, the 747 can be landed comfortably anywhere in the nominal 3000' landing area (first 1/3) of a typical runway. OTOOH, I think a "real" AOA indicator would be VERY helpful in escape maneuvers for WindShear and Terrain warnings. The stick shaker is a useful On/Off switch for backpressure, but a trend indicator via AOA would be much more useful. It's an interesting subject and I'm sure in any end analysis, aoa could be integrated into the heavy environment. more than it has been. Personally I like aoa. I've always taught wing and energy management flying from Cubs to high performance singles. The future may very well reveal the benefits of aoa to a wider cross section of the commercial community. Hope so anyway! :-) DH Referring to sims, I found the AoA indicator of scientific interest to measure airfoil performance, but in shooting landings I relied on the IAS (knots/hr) and vertical airspeed indicator(feet/minute), those together give a rough idea of angle of descent, and one then gets a feeling of AoA from pitch. What might be considered is an instrument that can provide all that info in nice clear form on single gauge at a glance, let's design it. Ken |
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