Aircraft Arresting Barriers

Technical parachutes

Subject list:

Artillery caliber illumination parachutes
Smaller caliber illumination parachutes
Plastic film parachutes
Brake chutes
Small target airplane recovery parachutes
Meteorological parachutes

Artillery caliber illumination parachutes

Below is for downloading a QuickTime/Cinepak-video. It presents the operation of one UOTILA plastic film parachute designed for this purpose. The whole operation time is one and a half minute long, The video speed is 2 frames/second.

This one stage parachute system consists of a single parachute. Its opening is controlled in such a manner, that the drag force does not show high peaks. Thus both the parachute and the carried load can withstand the heavy opening stresses of the high, yet subsonic speed. On the video the retardation distance begins from the first blow of smoke, which is caused by the ignition of the initiation charge. After the high velocity is slowed down in horizontal flight, the system swings down and motion continues in a stable vertical sink. When the illumination charge has burned to an end, the flight continues until the burned-down illumination charge with the parachute lands very near the spot where the video was filmed.

Download the QuickTime video by clicking the photo. The file size is 5.3 MB.

The video requires a QuickTime to play. In case you don't have it, the latest version of QuickTime can be obtained from here.

Back to top of the page

 

Smaller caliber illumination parachutes

Below is a photo, showing as an overlaying sequence of a opening test of an illumination parachute with a slug. The canopy shape develoment can be seen from right to left at 1/50 second intervals. As a result of these tests joint with live shooting tests, a stable and reliably opening parachute was developed for illumination purposes. A number of different sizes and types of these parachutes have been developed and manufactured, down to handheld rocket flares.

The preliminary tests do contain also different strength tests. Below is a test result from a small parachute suspension line seam test (to the parachute skirt). A rapid pull force is applied to the seam until it breaks and the result is recorded. Below a test shows the break value to be around 450 Newtons (45 kiloponds) or 100 lbs. A slow pull test cannot be used for parachute purposes, because it does not represent those stresses which appear during the parachute opening at speeds between 100 - 200 m/s, or 300 - 600 fps.

Back to top of the page

 

Plastic film parachutes

Plastic film as parachute material has certain advantages over conventional textile cloth constructions in certain aspects.

1.Smaller pack volume + less weight: The plastic film construction differ from respective textile cloth constructions. When the plastic film parachute is designed according to the advantageous properties of the material, it results in smaller pack volume and less weight than textile parachutes of equal performance.

2. One use only: Plastic film constructions do apply easier to automatic or semiautomatic manufacturing methods, providing more economic and also higher quality parachutes. The automatized parachute manufacturing lines are especially of advantage in the one-use-only parachutes.

3. Use in wet conditions: Plastic film parachutes can be repacked practically immediately after previous use, because the material does not absorb water and thus does not need drying before packing.

The very first demonstration was a plastic film brake chute in the late ´70's. The test pilot characterised this construction as having better stability and smoother opening than the original brake chute of the MiG-21 F. Yet the braking power, or aerodynamic drag was equal with both constructions.

In this case the crucial feature of this particular plastic film material was, that it could not withstand the remarkably higher temperatures in the brake chute compartment of the MiG-21 bis. This aircraft was the soon-coming follower of the MiG-21 F and thus the plastic film version could not be used with the -bis version, when the MiG-21 F retired.

Below are photos of different UOTILA brake chutes with both aircraft. Top is the plastic film UOTILA construction with the MiG-21 F and below is a textile cloth UOTILA construction with the MiG-21 bis.

MiG-21bis&uotila-parachute

This plastic film construction did follow the guidelines of the U.S. Pat 4,326,683 .This is an invention of Mr. Uotila where artificial porosity was built into the plastic film construction, in such a way that simultaneously both the parachute stability was good and its opening was smooth, ie. without any high overshoot.

The development continued with theoretical and practical studies joined with model and full size tests. One result was the U.S. Pat 4,993,667 . In fact, the above video presents a plastic film artillery caliber illumination parachute made according to the guidelines of this invention. A textile cloth construction of similar performance could not be designed to fit into the same volume.

Back to top of the page

 

Brake chutes

The braking power or the drag forces of the UOTILA brake chutes were measured in actual situation. Below is a typical graph of these results. The highest value is right after opening of the brake chute. This is the time of the maximum effect of the brake chute. The force rapidly decreases when the aircraft velocity slows down.

The same textile cloth UOTILA construction as above with the MiG-21 bis was designed also to fit and apply to the Saab-Scania Draken. The same chute had slightly less braking effect with the Draken than MiG-21 bis. This probably was due to the wake effect of the delta wing at small angle of attack.

Back to top of the page

 

Small target airplane recovery parachutes

See a photo sequence of a small target airplane landing with one of the UOTILA parachute designs.

Back to top of the page

 

Meteorological parachutes

The parachutes used in meteorology are characterised by the requirement of being capable to operate at large altitude range and have reliable and smooth opening characteristics at large speed range. Also this usage is expendable or one-time-only. These parachutes can be made of both materials, plastic film and textile cloth, depending on the needs. Below is an UOTILA textile parachute application for this use.

Contact info

A-Laskuvarjo
P.O. Box 130
Verkkomäentie 35
01801 Klaukkala, FINLAND
Tel: +358 9 879 3 878
Fax: +358 9 878 9 3040