Leroy R. Grumman Cadet Squadron

Civil Air Patrol - The official auxiliary of the United States Air Force

24 Hour Pack

The list below is the minimum required equipment for a ‘24 Hr Pack’ gear load-out.

1)   On your person:

 

a) Complete BDU/BBDU uniform with BDU/BBDU cap. The BDU/BBDU cap may be replaced by a hard hat

        or squadron ball cap based on mission needs

b) Notepad and Pencil

c) All CAP Identification, including CAP ID card, 101 card, First Aid card, etc.,…

d) Watch

e) Safety Vest (Hi-Viz Orange, Yellow or Lime Green)

f) Ground Team Member & Leader Reference Text

          (see "ES - Downloadable Resources" subpage)

g) Signal Mirror

h) Whistle

i) Pocket or utility-type knife, multipurpose with can opener

         (Swiss Army-type knives or Leatherman-type Multi-Tools are  recommended)

         (Fixed-blade knives are prohibited)

 

2)  Backpack, Web Gear/Load-Bearing Equipment (LBE), or SAR/Survival Vest containing:

 

a)     First Aid Kit consisting of the following:

 

(1) Antiseptic Cleansing Pads, 2

(2) Antiseptic Ointment

(3) Band-Aids, various sizes, 6

(4) Moleskin, 2” X 4”

(5) Roller Bandage

(6) Safety Pins, Large, 2

(7) Gauze Pads, 4

(8) Triangular Bandage

(9) Tape, First Aid

(10) Personal Medication if needed

     (your Ground Team Leader should be informed about what you have and where you carry it)

(11) Rubber Surgical Gloves, 2 pairs

  

b)     SAR/Survival Equipment:

(1) Flashlight, primary (with red, green or blue lens), with spare bulb and batteries

(2) Flashlight, back-up

(3) Waterproofed Matches

(4) Match Container, waterproof w/ striking surface

(5) Chemical Light Stick, green

(6) Compass, Lensatic or Orienteering (with "glow in the dark" dial markings)

(7) Nylon Line, 50' (paracord or simiiar)

(8) Flagging Tape, 1 roll

(9) Work Gloves, 1 pair

(10) Leaf Bag, large

(11) Duct tape, 5' - 10' length

(12) Insect Repellent

(13) Lip Balm

(14) Sunscreen

(15) CAPF 106 Ground Interrogation Form, blank, 5 copies

        (see "ES - Downloadable Resources" subpage)

(16) Disposable Moist Towlettes/Wipes in Foil Wrapper, 4

(17) Tissues/Toilet Paper

c) 2 meals

d) 2 liters of water carried in canteen(s) and/or hydration bladder(s)

e) Poncho/Rain Gear

f) Outerwear appropriate for mission/exercise conditions, if necessary (in pack if not wearing it)

g) Change of Socks

h) Shelter Material, preferably 8’ X 10’ (spare military poncho meets the need)

i) Cellular Phone, Calling Card, or Change for Phone Calls to contact Mission Base in the event of a comms radio failure

72 Hour Pack

72 Hr Pack consists of:

A complete 24 Hr Pack (see above) plus -

 

Water (3 – 4 quarts)

Food sufficient for 2 days

Extra Poncho

Extra Flashlight

Extra Compass

Shelter/Tent

Sleeping Bag

Sleeping Pad

Extra BDU/BBDU uniform

Extra Underwear

Mess Kit (including items needed to clean same)

 

Gear/Pack Information

When selecting your gear, consider functionality, reliability, and weight.

When selecting equipment for carrying your gear, consider how it will work in both cold weather situations (while wearing an M-65 Field Jacket w/ liner or ECWS Parka) and hot weather situations (see the eighth bulleted item on this list).

Store as much of your gear as possible in labeled/color-coded waterproof zip-lock bags or containers for protection and easy retrieval.

Make sure you have a complete pack, since missing items may result in you (and therefore your Ground Team) being unable to complete its' assigned mission (i.e., "I'm cold", "I'm wet", "I'm thirsty", "I'm hungry", "I'm bug-bitten", ...).

You may carry additional equipment subject to Ground Team Leader approval and your ability to secure and carry it – remember, you may have to walk a long way carrying it all.

Hand-Held GPS units are great to have, but not required.  They are not considered a replacement for the required compass (Item "2.b.6.") in the 24 Hr Pack, since electronics can fail and batteries eventually run out of charge.

Try to minimize any loops, lanyards, elastic cords or straps that may be hanging off of your uniform or pack since they may catch on heavy brush or undergrowth and slow your progress.  Note that lanyards for whistles or other items that are attached to the BDU/BBDU blouse or trousers are not authorized under CAPM 39-1.

If you decide to use a SAR/Survival Vest to carry your required gear, you should consider acquiring the vest in one of the specific safety colors (Hi-Viz orange, yellow or lime green). If your vest is any other color, you will be required to wear your Hi-Viz orange, yellow or lime green safety vest over it, possibly hindering quick access to your required gear, plus adding another clothing layer (T-shirt + BDU/BBDU blouse + SAR/Survival Vest + Safety Vest) that could be uncomfortable during hot weather conditions.

Gear weight is a major factor regarding comfort and injury. Other factors include a person’s conditioning and the design of the backpack or other load-carrying equipment.  The total gear weight should not exceed the following limits:

 

1. For optimal comfort only 25% of body weight should be carried.

 

2. Beginner Ground Team members should only carry 20% of their body weight.

 

3. Day packs without a frame, LBE and SAR/Survival Vests should not exceed 20 pounds.

 

4. You can carry comfortably 30-35% of your body weight using a properly loaded frame pack.

 

5. Never carry more than 35% of your weight. Properly trained, equipped, and highly conditioned personnel can exceed these guidelines as required.

 

Typically, Ground Team members set-up their equipment so that the smaller complete 24 Hr Pack can be attached to or placed within the 72 Hr Pack.  Depending on mission requirements, GT members will be instructed to use the 24 Hr Pack, the 72 Hr Pack, or utilize the 72 Hr Pack items to re-supply the smaller 24 Hr Pack as needed.  Since Long Island is primarily an urban/suburban environment, the 72 Hr Pack is rarely needed for LIG SAR Missions and SAREX's.

 

 

It makes sense to most people to pack the heaviest things in the bottom of the pack, but that isn't correct. A quick demonstration is all it takes to convince them that high and close to the back is best. It's all about center of gravity.

When standing normally, your body has a center of gravity running from your feet up through your head. There is the same amount of weight in front and behind and side to side of this imaginary vertical line. If you bend your head backwards, your hips move forward to counter the weight. If you lean to the left, your hips move to the right. Pretty simple.

When you plop a pack on your back that weighs 1/4 to 1/3 your body weight, you naturally need to lean forward to counter it. But, packed correctly, the amount of lean can be reduced resulting in more comfortable, upright posture while backpacking.

 

Place a heavy tent or dense food at the top, close to your back. When you lean forward a little, this weight crosses the center of gravity, helping to offset the rest of the pack weight.  Place that same tent low on the pack and you need to lean forward further to offset the weight.  The further out from your body a heavy item is placed, the more lean is required to offset it.  A heavy item to one side will require lean to the other side to offset.

Signal Mirrors

The signal mirror is the most basic and best all-around signaling device. Compact and simple to operate, it has been successfully used for many rescues. While any shiny object can and has been used for signaling, a purpose made signal mirror is generally brighter and the best are much easier to aim.

 

 

In normal sunlight, the flash from a good signal mirror can easily be seen for 10 miles and generally the flash will be visible up to 50 miles, depending upon atmospheric conditions. The record rescue from one is 105 miles, at sea. A mirror will even work on bright overcast days and with moonlight, though with much reduced range. Many experts recommend carrying two as you can then more easily signal in a 360-degree sweep with a little practice. An experienced user can signal up to 270 degrees, sometimes even a full 360 degrees if the sun is high, with a single mirror, but that is pushing it for most users.

 

 

(Note - CAP does not perform operations in "hostile areas", but you probably already knew that)

 

 

A mirror 4 inches by 5 inches (standard United States Coast Guard size) or 3 inches by 5 inches (standard large mil-spec size) is ideal. Anything much larger gets to be unwieldy and can be difficult to use for extended periods or to aim accurately. Even the USCG size can be awkward for those with smaller hands, especially if it is made of heavy material. The smaller 2-inch by 3-inch size (standard small mil-spec size) work adequately and the convenient size is an asset. There are also a few manufacturers that make mirrors even smaller than this. Generally, the bigger the better, since brightness is partly a function of the reflective area. The other determinations of brightness is just how reflective the mirror actually is and how uniform and consistent the reflected beam is, which is determined by its design, the materials used and its condition.

 

NOTE: You may see or hear about the recommendation online and elsewhere for the use of a CD-ROM as signal mirror. It is shiny, reflects light, has a hole in the center, and thus looks somewhat like a signal mirror. Moreover, many of us have lots of useless CDs around, thus its appeal.

 

In tests, a CD proved to be only about 20%-25% as effective (distance and brightness at distance, judged subjectively) as a 3 x 5 mil-spec plastic signal mirror, a bit more effective, but not even 50% compared to a small 2 x 3 mil-spec plastic signal mirror. It would compare worse against higher quality mirrors.

 

From an operational perspective, in an After-Action Report of a major SAREX (Search and Rescue Training Exercise) conducted in 2001 by the Colorado Wing of the Civil Air Patrol, the conclusions were, "that "victims" who had never used a signal mirror (with the aiming hole in the middle) were able to use them effectively, while CD's (AOL etc.) are useless as signal mirrors."

 

It also has the disadvantage of requiring two hands to aim it as compared to a signal mirror with an integrated aiming device and the hole is not an aiming device. The mil-spec plastic mirrors also float while the CD may or may not, and certainly not as well. Given that a good signal mirror is not very expensive and is the most effective daytime (sunlight) signaling device, using a CD hardly seems worth the savings.

 

This is not to say you couldn't be rescued using a CD. People have been rescued using the hologram on a credit card to signal with and the CD is far superior to that small reflective surface. A CD makes a decent improvised signal mirror compared to many other options and since they are essentially free, it may be worth carrying some for other members of your crew or party to use, multiplying your signaling capability. However, using a CD as a primary survival-signaling device is not recommended.

550 Paracord

Description

 

550 Paracord is a parachute cord used by the military that is strong, lightweight, and invaluable in many SAR situations. Military grade 550 Paracord is nylon Kernmantle rope known as Mil-C-5040 Type 3.  550 Paracord is 1/8 inch in diameter, has a tensile strength rated for 550 lbs., dries quickly and is mildew resistant.

 

As a Kernmantle rope type, its interior core (the 'kern') is protected with a woven exterior sheath or mantle that optimizes strength, durability, and flexibility.

 

  • The exterior sheath has a tensile strength rated at 300 lbs.
  • The interior core is comprised of 14 inner strings, each of which have a tensile strength rated at 17.5 lbs.
  • Pairs of inner strings are combined into a total of 7 internal strands, each of which has a tensile strength rated at 35 lbs.


Uses

 

Because 550 Paracord can be be broken down and individual strands removed and combined into your own configurations, it can be used as is or disassembled to be put to a wide variety of uses. As a general purpose utility cord, it can be used for (as examples):

 

  • Making a Shelter
  • Ridgelines for Tarps
  • Securing Equipment
  • Shoelaces
  • Vehicle Tie Downs
  • Sewing Fabric
  • Establishing Site Boundaries
  • Repairing Equipment
  • Clothes Lines
  • Equipment Lanyards
  • Anchor/Stake Lines
  • Splint Applications
  • Applying a Tourniquet

 


Colors and Lengths

 

Colors - Currently, there are many available 550 Paracord colors such as OD green, red, black, international orange, white and foliage green.

 

Lengths - Standard lengths of 550 Paracord available are 50, 100, 250, 500, and 1200 feet.  A cut length of 100 feet will typically cost about $10.00 at a local retail establishment, although you are likely to find good deals on the internet, especially if you purchase 550 Paracord on spools. A 1,200-foot spool of 550 Paracord can often be purchased for under $50.00. 


How Much Should You Have?

 

With respect to Ground Team activities when traveling on foot, weight and bulk are of prime consideration. As noted above, a 50 foot length of nylon cord is the minimum length required in your 24 Hr Pack (see the "24 Hr Pack" gear listing above). This is generally enough cordage to rig a shelter with enough length of cord enough remaining for other useful purposes.


Care and Storage

 

In order to prevent 550 Paracord from fraying, you can melt each end of the cord by holding it up against a small flame for a few seconds. Before each use be sure to inspect your paracord for nicks, frays and other potential weak spots.  As you cut and use sections from the paracord length that you have available, be sure that you replace the used portion with a full 50-foot length at your next opportunity. In a critical SAR situation it is preferable that you not have to splice sections of cord together in order to obtain a cord of sufficient length.


Braiding

 

Paracord braiding is a craft where paracord is braided into items that are of both decorative and functional value. Bracelets and lanyards made of paracord are common examples of paracord braiding.  These items can be unwoven for use in emergency situations.

 

 

 

Hydration Bladders vs Water Bottles/Canteens

 

Specifics

Hydration

Systems

Water Bottles

Or Canteens

Load Carrying

Water is one of the denser, heavier items (2 liters [67.63 fluid ounces] = 4.41.lbs) required as part of the 24 Hr Pack. Carrying it close to one's back (as when one uses the hydration pocket in their pack) is the best way to carry the weight.

PLUS

MINUS

Comfort

If packed incorrectly, the rigid bottles placed in a pack may end up sticking or pressing into your back. The hydration bladder is soft and flexible when placed in the hydration pocket in your pack on your back.

PLUS

MINUS

Convenience While On The Move

With a hydration bladder system, you can drink from the tube/valve while your are moving. With a water bottle/canteen, you may need to stop and take your pack/vest off, get your bottle/canteen out, unscrew the cap, drink, put the cap back on, put the bottle/canteen away, and ruck up once more.

PLUS

MINUS

Monitoring

You can't see how much you have left in a bladder without unpacking and then, once viewed, repacking the bladder.  Water bottles/canteens are more apparent with regard to amounts of fluid remaining.

MINUS

PLUS

Replenishment

Depending on the design, to load a full (refilled) bladder into a fully loaded pack can be difficult without unpacking the pack first to get the bladder in and positioned correctly.  Water bottles/canteens can be slipped into a pack or mounted externally on the pack or on a LBE belt or vest.

MINUS

PLUS

Container Weight

In terms of equivalent capacity when empty, hydration systems are generally lighter in weight than water bottles/canteens.

PLUS

MINUS

Container Bulk

An empty hydration bladder is flat when empty and, if desired, can be rolled up to save space. Typical water bottles or canteens occupy the same amount of space full or empty.

PLUS

MINUS

Durability

Hydration systems (bladders, tubes and valves) are more subject to ruptures, leaks, punctures, etc. than water bottles/canteens.

MINUS

PLUS

Maintenance

Hydration systems (bladders, tubes and valves) are more difficult to clean and maintain (see “Hydration Packs – Maintenance and Storage” section below), especially in the field, than water bottles/canteens.

MINUS

PLUS

Cold Weather

In sub-freezing conditions, the fluid that remains in the tubes and valves of hydration systems will freeze relatively quickly due to their exposed location when routed over the shoulder and fastened on the chest strap.

MINUS

PLUS

 

Hydration Packs - Maintenance and Storage

Cleaning Hydration Packs

 

How to Clean the Water Reservoir (Bladder)

 

·  Remove the reservoir from the cloth pack

·  Clean the reservoir with mild soap and hot water

·  Scrub the inside with a baby bottle brush

·  Air-dry the reservoir by suspending the reservoir upside down with the fill cap open.

Cleaning Solutions

 

·  A little mild liquid dish soap (cleaning)

·  2 teaspoons of liquid bleach (disinfecting)

·  2 teaspoons baking soda (removing odors)

If you are only using dish soap to clean the water reservoir, you can immediately wash, rinse, and dry the reservoir and tube. If you added bleach or baking soda to disinfect or deodorize the water reservoir, let the cleaning solutions sit in the water reservoir over night, and thoroughly rinse and dry them the next day.

How to Clean the Tube


Run one of the above cleaning solutions through the tube, and scrub it with (a) a long pipe cleaner, (b) a flexible wire covered with cloth, or (c) one of the specially-made brushes. Be careful not to puncture the tube.

How to Remove Odors


Fill the reservoir with water and add 2 teaspoons of baking soda. Let it sit overnight. Rinse thoroughly and air dry.

How to Clean the Cloth Pack


Many manufacturers recommend machine-washing packs in cold water with a mild detergent, and then letting them air dry. If your pack did not come with cleaning instructions, it's safer to hand wash.


 Storing a Hydration Pack


Dry Storage

Dry the pack thoroughly and completely before storing. This is the safest way to store your pack.

Wet Storage

Some people store their hydration packs in the refrigerator, filled with cold water, because the cold air and water will help to prevent contamination. 


 Hydration Pack Cleaning Tips

 

The most important thing you can do to keep your hydration pack safe and sanitary, is dry it thoroughly after each use to prevent the growth of mold, mildew and bacteria.

 

You can purchase special soaps, reservoir brushes, hose brushes, and air-drying hangers for hydration systems. You don't need to buy these products, but some of them will make the cleaning process easier.

 

You can make your own air-drying support/spreader device by modifying (cutting and smoothing) a plastic hanger.  The device will allow the reservoir to be hung so that the inside of the reservoir will dry out easier and quicker.  Make sure you smooth any sharp or pointed edges on the hanger before use so that the reservoir does not get punctured or otherwise damaged.  Do not use a metal hanger as it may rust and stain the inside of the reservoir.

 

 

 


It is best to use only water in your hydration pack. If you do use a sports-type hydration or nutrition drink in your pack, it is critical to clean and disinfect the hose and the reservoir afterward.

 

Some of the soaps people use to clean their reservoirs are dish (not dishwasher) detergent, denture cleaning products, and soaps made for cleaning baby bottles.

Binoculars

Even though they are not listed as required equipment, you should consider including binoculars as part of your 24 Hr Pack gear.  In open areas such as meadows and marshland, they will allow you to more easily identify distant objects.

 

Two numbers, such as 8x42 or 10x50, describe every pair of binoculars.

 

The first number refers to the magnification.

 

The second number is the diameter (in millimeters) of the objective lens (the larger, front lens).


Magnification

The higher the magnification, the more detail you see and the bigger the image you’re looking at.  However, the higher the magnification, the worse the effects of heat shimmer and any hand shaking. For otherwise comparable binoculars, the higher the magnification, the heavier the binoculars, the harder to focus on close objects, and the more rotations of the focus wheel to go from near to far.

The lower the magnification, the more of the scene you will see and, for the same size glasses, the brighter your image.


Diameter of Objective Lens


The second number describing binoculars refers to the diameter of the objective lens, measured in millimeters. Pocket or compact binoculars usually have smaller than a 32 mm lens and some are as small as 18 mm. This makes them wonderfully easy to carry around. To offset this advantage, they’re uncomfortably small for many hands and don’t work well under low light conditions.


Binoculars with an objective lens over 50 mm let in enormous quantities of light, making them more functional in low-light conditions, an advantage offset by their extra weight.


Most standard binoculars have an objective lens between 35 and 50 mm. Since magnification power also affects how bright your image is, a single line of binoculars tends to have larger objective lenses as the magnification power goes up.


Exit Pupil


The Exit Pupil is a number describing the magnified image in the eyepiece as it leaves the binocular to enter your eye. You can figure out what it is by dividing the size of the objective lens by the magnification power. That is, 10x50 binoculars would have an exit pupil of 5mm, and 7x42 binoculars would have an exit pupil of 6mm. You can judge both the size of the exit pupil and the quality of binocular optics by holding the binoculars at arm’s length and looking at the spot of light in the eyepiece. The larger it is, the larger the exit pupil. Exit pupil is one indication of how well you can see at twilight or at night. Brightness of the image is also greatly affected by the quality of the glass and the coatings on the lenses.

 

While looking at the light spot to judge the size of the exit pupil, pay close attention to how crisp it is. The sharper the edges, and the more perfect a circle, the higher quality the optics. To test whether the binoculars are properly aligned, hold them out or, better, set them on something level, pointed at a straight horizontal line such as a shelf, the line between a wall and ceiling, or a distant building. If the binoculars are truly aligned, the line should be at precisely the same level in each of the eyepieces.


Eye Relief

One number that usually isn’t featured conspicuously on binocular specifications but can be very important if you wear eyeglasses is Eye Relief. This is the measurement, in millimeters, of the optimal distance between your eyeball and the ocular lens of the binoculars. Binoculars virtually never have the eye relief written on them, but you can make a rough estimate by simply looking at the eyecups. Manufacturers design their eyecups to hold the binoculars at the right distance from the naked eye. No matter what the eye relief is, if you don’t wear eyeglasses you can extend the eyecups and they’ll be set at the proper distance for you. If you and everyone else who uses your binoculars don’t wear eyeglasses, eye relief won’t matter at all.


But if you do wear eyeglasses, you want to make sure that the eye relief is about the distance from your eye to the outer surface of your eyeglass lenses. Glasses with thick lenses or frames that hold them well out from your eyes require binoculars with longer eye relief than glasses with thin lenses in frames that are close to your eyes.


How do you figure out what the best eye relief for you is? If you have an opportunity to test out several different binoculars with different eye relief, you can see what the specs are on the binoculars that work best for you. Otherwise, you may simply have to make an educated guess.

Even if the eye relief doesn’t properly match your glasses, you’ll still be able to see through binoculars. But when the eye relief is shorter than it should be, your field of view will be narrower and the image will not be as large as it would be with proper eye relief–this is often called “tunneling” or “tunnel vision.” If the eye relief is longer than it should be, you may find yourself holding the binoculars slightly out from your glasses, making them harder to hold steady. Fortunately, more and more binoculars are coming with adjustable eyecups, allowing you to extend them slightly if necessary to hold them at the perfect distance from your eyes.



Binocular Design


At the same price point, the optics in porro prism binoculars are simpler and so usually higher quality than roof prism binoculars, so in lower price lines, porroprisms are sometimes the wiser choice. Porro prism binoculars tend to have good light gathering and depth of field, though they’re heavier, bulkier, and have an external focus, making them more vulnerable to water and dirt damage.



Field of View


Field of View is given either as the width of your view at 1000 feet, or as a number of degrees. Wide-angle binoculars give you a wider field of view, but unless the binoculars are expensive, the added field of view is often blurry. Wide-angle binoculars are heavier than comparable standard ones, and sometimes not quite as crisp.


Other Binocular Types

 

Zoom Binoculars - The zoom mechanism compromises optical clarity (though not nearly as much as in the past when manufacturers used less advanced coatings). Zoom binoculars are also heavier than comparable standard (non-zoom)binoculars.

 

Image-Stabilized Binoculars - make up for the shaking and distortion, but are bulkier, more expensive and weigh more than comparable non-stabilized models.


 

How to focus binoculars

1) Aim your binoculars at something in the distance.

 

2) Close the right eye (or cover the front of the right tube), and focus the left side of the binocular to your left eye using the center focus control, which is concentric with the pivot shaft between the binoculars. (Note: the left eyepiece itself does not focus on center focus binoculars.)

 

3) Next, close your left eye (or cover the front of the left tube), and focus the right eyepiece to your right eye. DO NOT touch the center focus control while you are focusing the right eyepiece to your right eye.

 

Now you are finished. What you have just done is adjust the binoculars for your individual eyes. (Practically everybody's left and right eyes are different.) From now on, you only need to adjust the center focus control when you look at things at different distances.

Night Vision

The retina in the human eye has two general types of light sensitive cells: rod cells for colorless night vision and cone cells for color vision.

Rod Cells:

In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as light is absorbed by them. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to white light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark.

Rhodopsin in the human rods is insensitive to the longer red wavelengths (measured on nanometers, or ‘nm’) of light, so many people use red light to preserve night vision as it will not deplete the eye's rhodopsin stores in the rods and instead is viewed by the cones.

Cone Cells:

The cone cells come in 3 varieties, one each for seeing red, blue and green light. Rod cells gradually become very sensitive to dim light after being in darkness for 30 minutes or so. They can become desensitized in a second or two of bright light. The only type of cell that is sensitive to red light is one type of cone cell. These cone cells allow you to see while using red light.

Since the rod cells are not sensitive to red light, they do not desensitize while you are using red light. Rod cells have various levels of sensitivity to all other colors of light and will desensitize when exposed to that light. When you turn out the red light and try to see in darkness, your rod cells are still sensitive (dark adapted), so you still have your night vision (dark adaptation).

That is true, but just because rods are not sensitive to red light does not mean that they will not be negatively affected by red light. The rods do not need to be desensitized to lose your night vision. Most red lights sold to preserve night vision are in the 625-630 nm ranges even though it takes a wavelength above 640 nm to really be beyond rod sensitivity. Lights with outputs of over 640 nm are rare because the human eye is so insensitive to that range that a light of that color would be practically worthless since it would be so hard to work with.

Even the common compromise wavelengths between 625-630 nm are so difficult for the human eye to utilize that there is always a tendency for red lights of any wavelength to be designed and/or used in too bright a mode to preserve dark adaptation.

As to the real effect of night vision with respect to the human eye, virtually any color of light, if it is dim enough, will allow the eye to see after turning it off. If the light is bright, no matter what color, you will LOSE your night vision!

The human eye is most sensitive to NVG (Night Vision Green)/aqua/turquoise light. As a result, you can see the most detail with the least/dimmest amount of light in this color. This is largely why night vision goggles display in shades of green; the human eye can see the most detail in this shade. However, the human eye is also the most sensitive to this color when it comes to losing your night vision. Red on the other hand, causes you to loose your night vision the least, (Note - not to be confused with not losing your night vision at all when using red, a common myth) but the eye cannot see as much detail with red light as with NVG. So the bottom line is:

  • Use only as much light as necessary to accomplish the task if you want to preserve your night vision, no matter what color you're using, and
  • You will need a brighter red light to see as much detail as you will with a dimmer NVG light. Given that you will have to use different intensities of light for the two different colors to see the same amount of detail, the net loss on your night vision will probably be about the same.

In summary, both red light and NVG light will preserve night vision, if the illumination is correctly set. However, NVG does it with less illumination and increased contrast, providing more clarity and detail.

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