One of the most misunderstood technologies in egress systems is the downward ejection seat. These were and are used in many different aircraft and as with all egress systems are the product of compromise. The ultimate egress system would be comfortable, protective, lightweight, easy to maintain, and allow great visibility among many other features. They are a product of their times, often 'cutting edge' technology or close to it. The compromises begin early in the process. For example the P-80 was nearly complete and finalized when the German He-162 seat was being tested and it was test fitted to the cockpit design. Instead, the first seat used in the P-80 was a similar seat, however it had many limitations in part due to the already designed small cockpit. It required jettisoning the canopy before ejecting and had no automatic features.
Over the next few years most aircraft were equipped with various upward seats but then in the mid-1950s aircraft with taller or 'T' tails began being designed like the XF-104. During the design phase the studies on the ejection seat indicated concerns that at higher speeds that the aircraft was designed to be flying at the tail would be a major risk to an ejecting pilot. Empennage problems had plagued the design of egress systems since the very beginning of their development. Aircrew would often strike parts of the airplane behind the cockpit on the way out and this could cause injury. The ejection seat in part was designed to help limit this possibility. The other reason to select a downward firing seat was due to space limitations in larger aircraft cockpit design. The B-45 and B-47 were fitted with downward seats as the third crewman was added to a lower deck in the cockpit. This meant the structure above would restrict the ability of the seats to get clear (unlike the Canberra which had two seats on a lower area but had a clear path to the top of the fuselage.) These craft were used as the testing for the downward seats and they were adopted readily for these aircraft. The B-52 when it came along also had the same issues and to this day fly with two crewmen on downward firing seats.
These bomber aircraft tended to be somewhat less risky in the low altitude area of flight and it was expected that most ejections would occur during high altitude cases. Therefore ejection into the ground was considered somewhat of an edge case.
Other experimental aircraft like the X-3 were designed with downward seat systems for various structural reasons as well. It used a motor to raise the seat into the cockpit for entry as the canopy did not open. These also were expected to not have many chances for low altitude ejection.
In the case of the F-104 the risk of striking the empennage was considered to be very high. The versions of ejection seats available during the early design process were limited to various catapult fired seats. The gun catapult had limitations on how much force could be used to fire the seat upward without causing physical injury from the ejection forces. The speed of the ejection was therefore limited to a point where the air resistance on the seat/pilot combination would decelerate to the point where the tail would impact them with a potentially fatal result.
Downward seat design had been used for various concepts in the past including on the XP-54 which used a
lever action to drop the pilot down and flip over to release him from the seat which remained on the lever.
This system helped inform the consideration for a downward system.
The advantages of using a lower powered catapult charge, a hatch that reduced the
complexity of the latching mechanism and the easier clearance of the empennage made it a potential choice.
The seat that initially was developed was called the 'B' seat (not to be confused with the F-106
Rotational 'B' seat.) This seat was like many of the time pretty rudimentary although it added a few
features for the higher speed including a set of ankle clamps and leg restraint arms to prevent leg flail
at higher speeds. Before ejecting the pilot would manually have to move his legs back and using his ankles
push back a pair of kick plates that would close the restraint around the ankle. Then pulling the seat firing
handles would cause the arms to be raised and the lap belt to retract. An interesting feature was the
ability to pull the handle a second time if the catapult cartridge didn't fire. This would release the
seat and allow it to freefall out of the cockpit.
This seat was quickly upgraded to a B-1 and B-2 model with engineering tweaks to increase function before the more common C seat was developed. The C was the first that would be easily recognizable as part of the C family and it included new side plates to help protect the feet from rotating in the windstream. The leg restraints were moved to the front edge of the seat pan and now included the arm nets to attempt to capture the arms and prevent arm flail. This change allowed for the inclusion of a reel system to retract the spurs worn on the pilots boots. Again these seats received engineering upgrades and became standardized as the C-1 downward seat (shown to the left.)
Ejection is always a last resort where staying in the aircraft is a worse choice. Should you eject downwards when the chance of dying is high? Is the chance in the aircraft worse? In most cases it is. Once the engines moved behind the cockpit as in jet fighters the cockpit became no longer safe to be in as it would crush or accordian as the engine and other mass behind the cockpit slammed into it.
Ejection leads to its own risk always. Ejection forces can injure, cockpit exit can be complicated by portions of the body contacting part of the aircraft etcera. The bigger concern in this case is the proximity with the ground. While modern seats feature Zero-Zero capability that refers to a zero airspeed, and at zero altitude (e.g. stopped on the ground fully upright) the seats of the time period when downward seats were selected this was not a capability that was available. To get to a zero airspeed capability the seats needed more force than a catapult cartridge could provide. This was solved when rockets were added but that is out of scope for this article, see this article instead.
Some seats were able to allow for ejection on the ground such as the Martin-Baker seats, however these were not typically selected for USAF aircraft at this time. Generally the manufacturers were using their own designs or choices for their seats based on USAF guidelines. These seats generally were configured with either seat pack parachutes or seat back parachutes. Both of these at the time tended to be inflated by opening the pack to release a pilot chute. This chute would provide enough drag as the aircrew moved through the air to withdraw the main parachute deployment bag. To do so required a certain amount of airspeed to produce the required drag. It also required a certain amount of distance to allow for the chute to be pulled out, inflate, and decelerate the mass to a safe landing speed. The distance required for this is generally around eight times the diameter of the parachute.
For a 28 foot parachute like the one often used in ejection seat packs this required slightly over 200 feet of distance. Complicating this math is the delay often used in ejection seat parachutes to prevent them opening too soon and entangling with or being damaged by the ejection seat. This is usually a time over one second from the seat man separation that arms the seat. In order to reduce this time during the low altitude period of flight the parachutes often used a 'golden key' to override the delay and instantly begin the parachute deployment. Therefore in order for a parachute to properly function on ejection at that low altitude region the aircraft would have to be traveling at a speed approaching the take-off speed of the aircraft, about 80-100 knots absolute minimum, and even there the risk is very high. For that reason ejection below several thousand feet was not recommended. Indeed for most aircraft even today the recommeded minimum ejection altitude is on the order of 10,000 feet above ground level if out of control. Lower levels to as low as 650 to 400 feet were listed in the manuals for controlled ejections depending on the parachute and timer configurations. While this may seem excessive for a seat capable of a zero-zero ejection there are other factors involved including such things as sink rate, and time to react to a malfunction in the system. Most seats of the time were considered out-of-the-envelope (OOE) if they were below altitudes like 500-2000 feet. This means that a safe ejection was not considered likely in that region. There are cases where people have survived OOE ejections but it is a high risk area. Still as stated above it likely is better than ground impact in the aircraft.
These considerations essentially level the playing field between upward and downward ejection seats. If you are traveling at take-off speed you should be able to pull up and roll inverted to eject. The upward acceleration of that action will increase the time and distance to allow for the seat separation and parachute deployment just as well as for an upward seat, with only the complication of the rolling of the aircraft. In a landing mishap there perhaps is a larger chance of not having the time for such a maneuver, however it is also just as likely that you will not have time to overcome the sink rate with an upward firing seat.
One other thing to mention in this section. The B-52 downward seat, which is still in use requires a minimum of 250ft in level flight for it to operate. The below photo is from a test done in the 1970s.
Based on the technology of the time of development, the downward ejection seat was a compromise, however the risk was not excessive compared to other seats of the period. It was somewhat riskier for certain, but the risk was considered acceptible. Of course as soon as seat rocket technology became available the F-104 was upgraded to the C-2 upward firing seat. This seat was a fairly successful seat, comparable to other rocket seats of the vintage. It evolved into the S/R-2 stabilized/retarded seat with a drogue, and its lineage continues today in the SR-1 seat that was used in the SR-71 and is still used in the U-2R/S fleet.
One of the main reasons the F-104 downward seat has a bad reputation is due to a statistic I have been having a hard time researching. There are believed to be some 21 fatal downward ejections, however the mishap data doesn't seem to support that due to the number of losses during the time period these seats were in service. A successful example of these seats was 'Suitcase' Simpson's ejection from a YF-104 after a tip tank damaged the tail. This was the second downward ejection from the F-104 family.
One particular failed ejection is often cited as a major example of the issues is the death of Iven Kinchloe. A well known pilot who flew X-2 and had been selected to fly the X-15. During a chase flight his engine failed on his F-104 and he ejected using a Lockheed C seat. It is believed he delayed in ejection due to the belief that he needed to roll the aircraft inverted before ejecting at low altitude. He ejected at some 2000 feet and the seat man separation occurred about 500 feet. Unfortunately his parachute did not fully deploy in time and he was killed (source. As you can see from the above discussion this should have been adequate, however for whatever reason the deployment was not in time.)
Thanks to Bryan Wilburn for reviewing and providing additional information for this article.
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