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Horten X flight tests:

In May 2 we met in J. Celman town. Tacchi, Figueroa and I prepared all the necessary for the first tow by plane.     
   
One of the things that we had made some days before, was to locate the parachute in the glider .   

This was a snub extra Swiltik, of back, with the detachable strap of the case with the canvas by means of two clamps.     
   
This case is held horizontally by two rubber bands, behind the main spar and under the plywood foil that forms the rib in the center of the wing.     
   
We had added two belts to the strap of the parachute whose free ends joined to each other and they took an ironwork that the pilot, once located in the booth, had to introduce in a security closing that is fixed to the board where he laid on the thorax.     
   
To get out of the booth it was only necessary to move a bolt and the pilot was set free.     

As the canvas of the parachute is fixed in the glider, every time one enters it to fly, it is necessary to hook the two clamps of the strap with the hoops of the canvas.     
   
Besides the speedometer, we prepared also a variometer, although the static one of  both are directly communicated with the booth so that the indications - of the variometer especially -  were not reliable, as I could check it later. The connection was made this way because according to the Dr. Horten explained to us, to obtain a good  static pressure it would be necessary to place a tube that should stand out more than a meter in front  of the leading edge of the wing, due to great chord of it.     
   
Another thing that we made was to place a support for the chin.     
   
This is an important detail , because if one doesn't have where to support the chin after a few minutes of be in prone position the muscles of the nape gets tired.     
   
Once the preparations were finished, we left with everything to the pave way.     
   
Eynard would tow my glider, so after coming to an agreement with him about it, I occupied my position in L'Alita and I made the sign that I was ready.      

The rope was stretching and we began to to slip for the floor. The speed was increasing until the commands began to respond and soon after it I took off. The speedometer continued ascending until the Fleet also took off.     
   
From this moment until I unhooked it is very little what I can say, because it was a perfectly normal tow, the same as in all the subsequent ones.     
   
With this I mean that there was not anything strange compared for example with a Grunau Baby.     
   
Only two things were different: first, the position; and second, the climb speed that was  notably superior to that of the Baby.      
   
The commands responded very well, being able to locate me where I wanted it just by moving a little the stick.     
   
The speed during the whole tow was maintained between 80 and 90 Km/h.     
   
The position was quite comfortable. The longest flight up to now has been of half an hour (between tow and free flight) so that one can not still judge this with certainty.   

In the first flight, however, the chin support was a little slack and when leaning on it I couldn't see the airplane that was below the horizon during the tow, so that to see it I needed to lift the head and this tired me a little. In the following flights I lifted a little the chin support and everything was O.K..     
   
As I didn't take altimeter with me, we accorded with Eynard that he would make me a sign of cutting when he arrived to about 800 meters.     
   
When I saw the sign I unhooked and the free flight began.     
   
I tested flight speeds from 50 to 100 Km/h. At these speeds everything was O.K. The commands were soft and they responded soon. There was not tendency to veer or to lean toward any side. Only when flying near 100 Km/h the stick spread to pull forward.     
   
I made turns of different inclinations. The turns in this machine are made very easily. It is sufficient to move the stick toward the side that is wanted to veer to and immediately the machine leans and it begins to rotate. This synchronization is obtained by means of the Frise effect of the aileron that goes up, and this has been enough exact because it has not been still necessary to modify anything.     
   
In the quick changes of turn it skids a little at the beginning but soon after it veers in contrary sense.     
   
The visibility is quite good and it is necessary to note that in this glider I  can look directly down from the covered opening with celluloid that covers the bottom surface of the profile.     
   
After making some more turns I was losing height and I landed.     
   
Certainly the first tows by air were made in completely calm atmosphere. This was checked previously by making a flight poll with a Baby. The caution adopted is necessary, being this a prototype, and one that I didn't know how it would behave in tow by air, especially as in this case of a machine in whose project one didn't had in mind this type of flight.     
   
After the first flight that I have related, that same day I carried out other more.     
   
This time we made turns a little more closed during the tow, without any trouble. Also as the chin support was now higher I could see the towing airplane well without having to lift the head.     
   
We arrive to about 800 meters and I unhooked.     
   
I was increasing the speed until arriving to some 120 Km/h and vibrations didn't take place neither in the structures nor in the commands. Then I tried the minimum speed and when taking the whole stick back the speedometer marked 50 Km/h. However this is not the minimum speed. What happens is that we should increase the up-end of the ailerons, because at 50 Km/h the commands respond well and still there are not indications of  loss of speed.     
   
This is one of the reformations that should be made.     
   
Then I tried to veer slowly. I moved the stick toward the left until the glider was inclined about 30° returning it then to the center and getting up to the maximum to the same time. In that position of the command the Piernífero veered at 60 Km/h maintaining the inclination and the flight line exactly as at the beginning. I made this way 5 or 6 turns without moving the stick.      

The turn of 360° was made in 12 seconds. But this time can be decreased by flying at a lower speed, and to do so there will be to increase the up-end of the ailerons.     
   
As everything went O.K. I decided to make a looping.     
   
I dived up to 110 Km/h and I pulled smoothly the stick, but it was too soft so that it was a very hung looping. I happened to reach the vertical but a stall originated rotating quickly the wing around the traverse axis until being with the nose toward the floor. Here it stopped the rotation and began a dive. As the speed built up I was getting up slowly and when it arrived to 120 Km/h I pulled the stick again to make another looping. This was what you could almost call looping, and it was also left hung although not as much as the previous one.     
   
Although we had tested the main spar in the workshop during the construction and that it was very resistant, in these first looping I had gotten up very smoothly so that the accelerations were the smallest possible.     
   
After this I made some turns and I was losing height.     
   
When facing the way to land I tried to bow the stick to one and another side. This maneuver, similar to the denominated "coordination of   commands", substitutes in this machine the slipping that is practiced in conventional machines without brakes.     
   
As L'Alita has simplified commands, these cannot be crossed to slip. However if the stick is leaned strongly in alternate form from one to another side, the machine oscillates around the longitudinal axis and as this is done relatively quick, the Frise effect is not enough to make it veer and only they produce small oscillations around the vertical axis so that it can stay the same direction. And these abrupt movements cause turbulence that increase the descent speed, being equal to a slip.     
   
This maneuver doesn't present any risk, because I have proved that is little what the machine crosses, still when the lateral inclination passes 30° so that it doesn't end up being unstable.     
   
It is necessary to be very careful with the flight line because if a loss of speed takes place at so little height and the machine is lean to one side, the consequences can be unpleasant,the same in the case of a hung slip. Also with strong wind it will be better to straighten out at height, since a gust can place the glider in a dangerous position.      
   
After "sliding" I landed concluding the last fly of that day.     
   
One week later, that is to say on May 9, we met in the morning in J. Celman again.     
   
This time we made comparison flights between our prototype and a Baby IIa, with booth closed. I clarify this last, because there is yield difference between a Baby with closed booth and one with windshield only.    

The closed booth can increase the glide relationship from 1:17 to 1:19.     
   
To be able to assure this we would be able to make the necessary  exact measurements so what we say is only a probability, based upon measurements carried out in Finland with a glider Pyk-5, of similar characteristics to a Baby, and one in which that relationship increased of  16,5 to 19 by careening the booth.     
   
For our comparison I have supposed then that the Baby with closed booth has an optimal relationship of glide of 1:18.     
   
That day we made double tows. In the first one I flew L'Alita and Eynard flew in the Baby. The towing pilot was Rodriguez.     
   
For further security we used ropes of different long. That one of the Baby had about 80 m. and mine 120 m. more or less so that the Baby would be always forward and I would be behind and to a side.     
   
This was an interesting experience, where I confirmed the good qualities of our glider for the tow by airplane.     
   
The tow was carried out without any trouble and it was enough to bow very little the stick to stay in my position to a side of the airplane.     
   
Previously we had suited with Eynard that he would cut first and that we would make glides at different speeds beginning with the minimum one of the Baby.     
   
When we reached 650 meters he cut and I followed it.     
   
We maintained south direction, with a speed of 50 Km/h, and a distance of 30 meters separated us. Soon after noticing that the Baby went staying above L'Alita, what evidenced that its speed of descent was smaller, we kept increasing the speed from 10 in 10 Km/h, but as now the BaBy was above me, it was impossible to say if the difference of descent speed increased or  diminished. We arrived to 80 Km/h. and still was noticed a difference in favor of the Baby.     
   
As the height was little, we separated. Eynard made some aerobatics and then landed. I landed after him.     
   
Then I made a double tow with Picchio. This time we reached 1.100 meters.   

We cut and began long glides and in straight lines with north direction, with speeds between 50 and 80 Km/h, in the following way: at 50 Km/h we flew separated about 30 meters, until it was noticed clearly that the Baby stayed  up. This lasted nearly half minute. Then Picchio slipped until reached my height and we increased the speed to 60 km/h, repeating the previous maneuver.     
   
In this way we was increasing the speed until arriving at 80 Km/h.     
   
The height was insufficient to continue, so that we had to separate and land.     
   
I made the following tow with Eynard.   

We reached a height of 900 meters and we tested  from 80 Km/h to more than 100. Here it was noticed that the difference in favor of the Baby was quite smaller. When we flew at 100 Km/h, it was higher than me and a little behind, so that it could not be judged exactly, but I found that at this speed the difference of height was not increased. Eynard said the same.     
   
The last comparison flight was made with Rodriguez. We ascended up to 1.000 meters and began the glides at 100 Km/h, with increasing of 10 in 10 until arriving at 140 Km/h. At this speed my machine flew very calmly. I didn't notice vibrations of any kind. On the other hand the tendency of the stick to leave forward had  increased and it was notable enough. If in this flight situation I had loosed the stick, I believe that the glider would positioned itself in a vertical dive soon after.     
   
In this range of speeds it was evident that those two machines worked very even.     
   
With this we finished the comparison flights.     
   
Before exposing the consequences that we can take out of these flights, I want to clarify that these measurements can only be taken into account to have an approximate idea of the flight qualities of the H - X, just as they are to the time being.     
   
Although the air was very calm down, indispensable condition for the comparison, it is necessary to carry out many flights before being able to assure anything, also these should be carried out at higher altitude to have ample time to test and to take better advantage of the flight, because below 500 meters you only can follow the measurement if both machines are well located with regard to the pave way. Below 300 meters you can't continue any long.     
   
After the comparison flights one can say the following: until 100 Km/h, the speed  of descent of L'Alita is bigger than that of a Baby with closed booth. At this speed they balance. Above 100 Km/h, the advantage is of L'Alita.     
   
This in fact doesn't represent an advantage because it is known that it is not worthwhile to fly with a Baby  in distance flights at that speed, except if it is in a field of strong ascendants as it could be in a good storm front.     
   
However, it demonstrates that the curve of  performance of the H - X is more spread than the one of a Baby, and yes, that it is interesting, because it happens the following: at the moment L'Alita has a fixed landing gear (a skate) and in the central inferior part it has an opening of 60 cm by 80 cm, through which the pilot enters. These two factors evidently increase the speed of  descent, because the turbulence that they cause is quite appreciable.     
   
So that closing the inferior opening by means of a light panel and installing a retractile skate, for example, it is evident that they would improve the performances. As the speed curve is more spread than that of a Baby, if at 70 Km/h. they coincide, at higher speed the advantage would be of L'Alita.     
   
All this is hypothetical. The time must decide.   

When the test flights are finished and let us get the definitive certificate of  navigability , again we will begin to worry  for those yield improvements, since the primordial it is that the machine fly well in all instances.     
   
As a result of these flights we decided to carry out the following reformations:     
   
Amplification of the booth, lifting some centimeters the arch where the celluloid is taken to allow the pilot bigger freedom of  movements. For this cause Scheidhauer, tests pilot of  Dr. Horten, could not fly; because he is something stouter than me and he was unable to enter well in the booth.     
   
The front part of the arch will be lowered some centimeters to improve the visibility, especially in tow.     
   
The windshield will be redrawn stretching it toward behind the wing. This is with the purpose of diminishing the effect of instability that a surface that is placed before the center of gravity of the machine causes when one blast acts on its side .     
   
We will increase the up-end of the ailerons acting on the command cables to be able to fly slower, especially in turns.     
   
To attenuate the moment of diving that one begins to notice passing of about 80 Km/h. we will place in the ailerons fins of aluminum of 30 cm long that stand out 6 cm. of the trailing edge, and bowed down about 20 degrees. This has been recommended by Dr. Horten to us.     
   
Up to now, this is more or less, all that I can say of the first tows by air.     

 
Rogelio Bartolini

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