There are many reasons for my writing this. Airplanes are getting so large that it seems unconscionable to needlessly ignore any hazard. I also wanted to leave something of importance to my pilot colleagues with whom I have had the pleasure to fly all my life.

Typically, while beginning a descending approach in an increasing headwind, as the pilot manages the indicated airspeed (IAS) just as he was taught; the airplane's actual speed energy is continuously reduced without his knowledge. Reaching a lower altitude, the airplane enters a new stratified layer of headwind air moving much slower and giving a large sudden reduction in headwind component. The resulting airspeed reduction gives a sudden uncontrolled increase in the rate of flight path descent, and a severe ground impact occurs before a climbing flight path can be established. An encounter with this combination of air movements, even by an extremely competent pilot, can produce a deadly accident since there is no alternative to the unexpected lift reduction from the reduced speed of the air over the wings. A complete reversal of all these air movement changes can cause a runway overrun, and if the runway is wet this type windshear accident is usually blamed on hydroplaning. It can be just as deadly as the first windshear combination as described above.

The common practice of using an IAS speed target alone for controlling the approach speed then becomes a significant part of the problem, since either type of windshear condition is totally unrecognizable and unknown to the pilot until too late for recovery. Using my system the pilot can monitor the actual approach speed energy relative to that which will be essential ahead in the landing environment of the runway or shipboard deck. This gives the pilot confidence by managing the actual final approach speed energy as well as the IAS. Using a single fast/slow instrument is necessary in the event of turbulence, which is sure to exist in that changing unstable air. Controlling the actual GS has never been possible until the use of INS or GPS, and the value of using an IAS/GS management has never been possible until that actual groundspeed information became available. Briefly, my background is presented below to give you some confidence in the judgment of my words.

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

I first soloed the day after my sixteenth birthday in 1938, and I flew light airplanes until enlisting as an Aviation Cadet in the U. S. Army Air Corps the day after the Japanese attacked Pearl Harbor. I was 19, and after Cadet training I flew 4½ years as a US Army Air Corps Pilot during WW II. Following my discharge in December 1945, I flew for The Flying Tiger Line, 6 months as a Co-pilot and nearly 33 years as a Captain; the last 8½ years in Boeing 747's. Retiring after flying in excess of 50,000 hours without blowing a tire or scratching an airplane, I have witnessed many advances for avoiding hazards. I believe the most important one remaining is called "Low altitude windshear on the final approach." Rarely encountered even in all-weather airline flying, it is usually fatal to many.

The purpose of this writing is to re-introduce my method of managing this previously unsolvable problem. My solution is made possible by using the actual GS information from a global positing system (GPS) or an Inertial Navigation System (INS). The pilot manages the IAS as usual, but with the additional requirement to control the actual GS to never be less than normal relative to the landing runway or shipboard deck. It assures arrival over the runway or deck threshold with sufficient IAS to remain airborne with actual groundspeed not too excessive for the airplane to stop before reaching the end of the landing surface. Protection from either hazard can never be assured using only a conventional IAS target speed since either a significantly excesive headwind or tailwind aloft can lead to a catastrophe after entering the environment existing at a low altitude in the landing area.

As an example, I landed my Flying Tiger DC-8/63F with near maximum landing weight on the same JFK runway 22L less than eight minutes before the tragic Eastern 66 windshear crash. After leaving the runway, I reported the severe windshear condition to the control tower and suggested they change the traffic direction to land toward the Northwest to avoid just that type of accident, and my advice was ignored. In my opinion, any pilot using the traditional IAS approach speed as that Eastern pilot had to use without actual GS information, would crash in the same windfield I had penetrated. Turbulence interfered considerably with my approach, but we survived only due to my use of the windshear defensive procedures described as follows:

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CCopyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

Since all of our airplanes were used on both domestic and international routes, they all had Inertial Navigation Systems (INS). After using INS for so many years all over the world for navigation, I learned to recognize a low altitude dangerous wind condition from their information, and I developed a procedure for defense against that type of windshear. It begins by calculating the actual approach normal GS expected ahead on landing detected by the GPS or INS;

Resolve the target approach IAS from the airplane performance charts as normally done, using the expected landing weight and, Convert that IAS to a true airspeed (TAS) using the airport elevation and surface temperature, then, Apply the expected along-course landing wind component to the runway/deck TAS to get a normal approach and landing target GS. The pilot then manages the actual approach speed to equal the lesser of: A. — The target GS, or B. — The target approach IAS.

AUGUST 2nd, 1985: The wreckage of Delta Air Lines Flight 191, a victim of Low Altitude Windshear on final

The normal wind increase with increasing altitude usually requires an approach using the more easily managed target GS, with the IAS equal to or in excess of normal. The GS and IAS targets are predicated on normal speeds in the runway/deck environment, so both speeds will be very near their normal for landing. The pilot should consider rejecting the approach if an actual tailwind GS exceeds its target by 10 kts or more.

Approaching JFK that afternoon, a thunderstorm was in progress along the final approach path and my target IAS was 143 kts with a target GS of 138. Precise speed control was impossible due to the turbulence and worse, the inconvenient location of my INS GS indicator was down near my right knee, far from my normal instrument scan, especially at that busy time. At 400 ft AGL the IAS was raising through 190 kts, 47 in excess of my target IAS, and the INS GS was reducing through 120 kts, 18 less than my target GS. We broke out into clear air at 300' AGL where I pushed all throttles forward to the stops as the IAS dropped and as we simultaneously weathercocked near 30º to the left. Over the approach lights where Eastern 66 was soon to crash, we had near 30º right drift with our airplane gyrating around in the turbulence so violently I barely had sufficient control to keep it airborne after passing over the runway threshold.

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

When the turbulence subsided, I kicked full right rudder with nearly full left aileron and simultaneously pulled the throttles into reverse as the port side wheel bogies contacted the runway. Ground spoilers did not deploy since their automatic operation was disarmed by the full throttle position back at 300 ft AGL. Our safe arrival was due more to luck than skill, and had I not pre-trimmed so much nose-up with the alternate trim levers while using so much forward elevator control pressure from the high IAS, it would not have been possible to have had sufficient up-elevator control left to remain airborne over those approach lights.

Capt. John H. Bliss testifying before the NTSB on the crash of Eastern Air Lines Flight 66, 1976

My procedure had so obviously saved us that I designed and patented (example follows) a method to mechanize a flight director fast/slow needle and auto-throttles to automatically manage the approach speed to my described parameters even in turbulence. If Eastern 66 had had such a system it would have saved them and they could have successfully abandoned their approach as they so obviously attempted from their flight data recorder information. If I had had my "Fast/Slow" speed control system, I'm certain my approach would have been managed far more precisely in the turbulence and with the extra 65 knots IAS I would have easily recognized the IAS and GS danger early enough to safely abandon my approach, and I would have had the speed energy to achieve it. All these details were confirmed by information on both my flight data recorder and that from Eastern 66. I have copyrighted all this writing since my speed control system's value has never been recognized.

The GS detection system I used was an Inertial Navigation System. Two are required on each aircraft, so each airplane has a minimum of a million dollars' worth of navigational systems. More recently, a GPS system gives equal or better GS information at a fraction of that cost. GPS can be used for detecting actual GS at such a low cost that it can be suitable and practical for use in all licensed airplane types. I used it in my Piper PA- 24 Comanche, Flying Tiger Boeing 747, and Douglas DC - 8, as described here. The approach calculations (IAS to TAS) should be completed before entering the landing area, or done automatically as indicated in my patents, so that all you must do to complete the process is apply the runway surface wind relative to the landing direction. This also may allow an adjustment as late as practicable before landing.

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

Pilots are trained to believe they have complete control of their airplane and its airspeed. This is generally true but in the windshear case, it can be hazardously compromised. It is crucially important to recognize that the pilot of Eastern 66, while flying accurately within approved practices, was led into a hazardous position from which he had no possible way to save his all-important passengers. The standard practice of using only the IAS to control speed energy on a final approach can place the airplane with insufficient speed energy in any excessive headwind. This can happen so insidiously that the pilot is not aware of it, and in the event of a severe headwind reduction near or in the landing environment, flight path control is removed, and the speed energy remaining can then be so insufficient that recovery is impossible. All this hazard can only be avoided by eliminating the earlier speed energy reduction regardless of any other instrumentation. GPS is so economically available to provide this accurate and up-to-second actual speed energy relative to the landing surface, there seems no excuse for not providing GPS to eliminate this remaining GS speed energy hazard.

Control of the speed energy is required before encountering any low altitude headwind change to avoid a runway/deck undershoot or overrun condition. GPS can provide the universally and economically available actual GS energy control for this type approach speed management, and it should be required for all licensed airplanes. It is certainly as important as the compulsory Kolsman window is now on all licensed airplanes.

This writing began with a description of my most hazardous low altitude windshear encounter. I believe that hazard was actually the result of an encounter with a mini-tornado, which is not typical of most low altitude windshear encounters. Though I have no records of other encounters, most have not been a major problem due to my procedure and the rarity of those that have been serious is an important part of the problem itself, since most windshear accidents have occurred resulting from an airplane unexpectedly entering a new layer of stratified air moving at a new reduced rate of speed or direction relative to the landing runway or ship deck. There's no prior warning or method of gauging the degree of danger ahead, and the reduced airplane accelerate/climb performance in a continuing headwind reduction during recovery is not as obvious in the more modern digital type analysis as is obvious using old fashion vectors. No two types of encounters are alike, obvious in the following.

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

Approaching Newark, N. J. late one very dark night in a DC-8 with near maximum landing weight; the ceiling was 900 ft overcast, visibility 12 miles with the surface wind calm. A cold front had previously passed, leaving a Boeing 727 stuck in the mud next to the ILS runway 04, and all the runways were very wet with standing water covering nearly half of all runway surfaces. The tower advised us of the runway conditions and cleared us for an ILS approach to runway 04 with a circle to land on runway 28, the shortest runway on the field. It was just long enough for us to land on with our heavy gross weight when dry. Everything was normal during the approach except while descending through about 400' AGL on my final approach, my actual GS was 42 kts in excess of my target GS. I abandoned my approach and pulled up to circle and land on runway 10. If I had landed on runway 28, I'm sure we would have touched down with the actual GS far in excess of normal and we would have hydroplaned right off the end of 28.

Next, Inbound from Tokyo early one morning over the Anchorage, Ak. outer marker while flying a Flying Tiger Boeing 747, we were cleared for an ILS approach to runway 6R. The surface wind was calm, and while flying my normal pre-calculated GS of 145 kts, our IAS was 225 kts, 80 kts in excess of normal. During my approach, while continuing with 145 kts GS, my IAS progressively reduced to 190 kts with 15º left drift when I first saw the approach lights. We were just above 300' AGL and the IAS dropped to a normal 145 kts where the drift vanished as expected. The landing was normal, and nearly a half hour after departing for SFO, I heard from ATC that a Learjet had crashed between runways 6L and 6R at ANC. After landing at SFO I learned that the Learjet had been flown by a very experienced and respected pilot, and the wife of a U. S. Senator onboard had been killed. I am convinced the pilot flew his airplane well within all accepted practices and procedures, but I'm also sure he did not have the advantage of the actual procedures made possible by using a GPS GS as described here. The use of actual groundspeed information to avoid the dangers of landing short or overrunning a runway or aircraft carrier deck can be essentially eliminated by using these IAS/GS procedures. The conditions ahead could have been continuously monitored by that pilot and he could have monitored how well it was corrected for before the actual windshear encounter.

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

Finally; Approaching Kaitak Airport at Hong Kong while flying a Flying Tiger Boeing 747, making a "Checker Board" approach in some very windy and turbulent weather. The airport is located in an area completely surrounded by mountains and very tall nearby buildings. The approach consists of making an ILS approach with an inbound track of 89º to a large checker board sign on top of a hill, then when you get down to nearly 350ft AGL you make a right turn and either land on runway 13 or climb out on a 130º track to go around on the back coarse of another ILS serving runway 31. A very large mountain stands just East and North of the airport boundaries and the surface wind was from 90º at 45 kt, gusty to 70. That type wind blows down across the eastern mountain, then across runway 13. My point is that I had no problem making my approach and landing while using my GS procedures, but Hong Kong Area Control closed the field for arrivals after the next two airplanes behind me proceeded to their alternates due to the turbulence and difficulty in maneuvering during their approaches.

Capt. John & Patti Bliss at the Flying Tiger Reunion in Sacramento, CA, 2002

These stories describe only a few of the more significant low altitude encounters with windshear I have personally experienced. Without using the actual GS information and my described procedures I would have had to use the same IAS procedures as the Eastern 66 pilot had to use, and there is no possible way I could be alive to relate all this information to you. These are only a few of the obvious advantages available to one using my system, but there are many others. As for example, I have noticed how the Navy airplanes making practice approaches at San Diego make many large continuous thrust changes on the final approach. It seems quite obvious they are using an auto-throttle, which is chasing the IAS changes, and most of these changes are superfluous in controlling the actual airplane speed energy. All these thrust changes disturb the pitch balance that interfere with the desired airplane stability on the approach. The GS can easily be controlled to the correct actual speed which will be required in the landing wind environment and it will not only protect against low altitude windshear hazards, it enhances the stability and accuracy of the approach with all its many advantages.

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

An addendum: In the copy of my patent included on page 8, the item "C" can be eliminated with line 123 joined directly to line 110.

Capt. John H. Bliss
The Flying Tiger Line (Retired)
jpbliss@mchsi.com

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

The Bliss Airoborne Low Altitude Windshear Defense System

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Copyright © John H. Bliss, 2007. No part of this document may be reproduced, stored on any retrieval system, or transmitted in any form by any means — electronic, mechanical, photocopying, or otheriwse — without prior written permission from the author.

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