Transcript of YouTube Video: The Insane Engineering of the F-117 Nighthawk

two f-117's are approaching their target

Over Baghdad below the cloud cover radar

guided surfac to- aair missiles scan the

sky for signs of an imminent threat but

see little more than a small blip that

Fades into the background of noise the

payload bay doors open revealing two

gpsg guided missiles destined for the

assumed location of the then Iraq

president Saddam Hussein this simple act

May well have revealed the stealthy

aircraft to radar below its exterior was

molded by precise mathematical equations

every facet designed to disperse and

absorb the electromagnetic energy

surrounding the skies around them with

the missiles delivered and their

location potentially given away the

defenseless planes quickly turned to

escape enemy

airspace this was a highly specialized

aircraft designed to carry just two

missiles in its payload Bay a plane that

looked like a fighter jet but if it met

enemy Fighters the subsonic plane armed

with bombs meant for ground targets

stood little chance it relied entirely

on stealth to Get Behind Enemy Lines and

strike without being seen something it

did time after time during the Gulf War

striking

1,600 high value targets without losing

a single

aircraft the design began as a simple

Diamond that aerodynamicists of Lockheed

skunkworks dubbed the hopeless Diamond a

template for stealth a shape that the

famous former skunkworks leader Kelly

Johnson doubted would ever be able to

fly turning this concept into a

functional aircraft would take the very

best aerodynamicists propulsion

Engineers Structural Engineers and radar

Specialists that Skunk Works had to

offer they carefully chipped away at the

simple but revolutionary shape to form a

masterpiece this is the in engineering

of the f117

Nighthawk the f-17 nigh Hawk's Journey

began here on the desk of Ben Rich the

newly appointed director of Skunk Works

taking over from the eminent Kelly

Johnson this paper a Russian scientific

paper translated by the Air Force's

foreign technology division held the key

to a new generation of aircraft war is

an Ever evolving game of cat and mouse

and in the past decade aircraft had

switched roles from Predator to prey the

development of Soviet radar guided

missiles caught the US industrial

machine by surprise a sudden realization

during the Yong kapor War of

1973 Israeli Pilots armed with the

latest and greatest American attack

aircraft lost 109 planes over just 18

days these planes were mostly shot down

by Soviet supplied surfac to- a missiles

supplied to the Egyptian and Syrian

armies these Crews required a fraction

of the training that was required to

train a fighter pilot and the systems

themselves were vastly cheaper the

Russians had invested billions into the

development of radar guided surface to a

missiles like the

sa5 these missiles could reach

125,000 ft in altitude and could even be

armed with nuclear warheads to blast wbe

Raiders out of the sky the extreme

altitude would mean Russians on the

ground would be shielded from the Heat

and shock waves and the Strong Winds of

the upper atmosphere would carry the

Fallout to Western Europe the

effectiveness of these missiles was not

down to speculation the balance of the

battlefield had shifted towards the

Soviets Air Force planners extrapolated

these attrition rates out to a full war

with the Soviets in Eastern Europe and

they saw the writing on the wall the

Soviets would wipe out the entire US Air

Force in just 17 days two strategies to

counter this advancement emerged

conventional wisdom of the time pointed

towards designing a plane specifically

designed to hug the terrain to be able

to fly longrange Missions at extremely

low altitude hiding from radar in the

ground clutter this resulted in the B1

Lancer its variable sweep Wing allowed

it to tailor its aerodynamics for both

low speed low altitude flight and

highspeed high altitude flight however

that was system would soon be challenged

thanks to one brilliant scientist Dennis

overhauser who on one fateful day placed

this paper on the desk of Ben Rich a

long technical document full of

complicated equations and theories but

for Dennis skunkworks radar Dome expert

it held a treasure the key to unlocking

a new way of Designing aircraft a method

to calculate the defraction of

electromagnetic waves stealth design was

not a new concept the sr-71's first

flight predates the first day of

development of the F-117 by over 10

years and it Incorporated some early

concepts for stealth that were largely

based around the laws of physical Optics

reflection and refraction avoiding

Corner reflectors was a known method to

reduce radar signature long before the

F-117 was theorized what this paper

unlocked was much more complicated once

thought to be too complicated to solve

defraction imagine waves approaching a

harbor Breakwater it's designed to

Shield the boats inside from the energy

of the sea with just the laws of

reflection the boats should be

completely unaware of the presence of

waves outside these walls and yet

through defraction the waves find their

way inside this is a messy chaotic

problem with too many variables to

consider for simple analysis and it only

gets more complicated with

electromagnetic waves but this paper

unbeknownst to the Soviets who allowed

it to be published internationally held

the key to the technology that would

allow aircraft to become the top

predator once again Ben Rich the newly

appointed leader of skunkworks under

pressure to take the Reigns from Kelly

Johnson approved a computer program to

be developed and within 3 months a

working program that allowed simple

shapes to be analyzed was created dubbed

echo1 allowing them to theorize the

Hopeless diamond this was of course not

a plane it lacked everything a plane

needs to fly it had no control surfaces

no propulsion no payload it even lacked

a wing Dennis was not an aerodynamicist

he was skunk's Raad home specialist

designing the nose cones that housed

their planes radar this design was a

template that could be molded by the

most skilled sculptors in aviation step

one was to figure out its Mission

profile this would decide several things

Max payload range and propulsion with

stealth a priority the F-117 could not

have external hard points this was going

to limit its weapons capacity it would

feature two internal weapon spays and

the plane would be a Precision bomber

its weapon of choice were laser guided

missiles inside the nose of the aircraft

hid a steerable turret containing a dual

field of view infrared sensor while a

second infrared sensor was located to

the right of the nose wheel well and

both sensors came with a laser which

could be aimed at the Target to guide

the missile with extreme Precision the

sensors locked onto and track targets

with help from the internal navigation

system switching from the

forward-looking to the downward looking

systems as it passed over the target

these systems were of course heavily

weather dependent as the plane could not

guide the missile through cloud cover

but GPS guided missiles were also an

option these were the only weapons on

board the plane would be completely

defenseless to aial threats and would

thus rely completely on stealth and

because of this the F-117 was going to

be a subsonic plane producing a sonic

boom was a good way to be detected not

by radar but just any person in the

general vicinity higher speeds also

results in increased aerodynamic heating

that could allow the plane to be

targeted by infrared guided systems so

the engines didn't need afterburners or

specialized engine inlets to slow down

supersonic air flow this simplified

engine selection and the General

Electric j85 was selected for the half

blue demonstrator which would later be

upgraded to the General Electric f404

from The fa18 Hornet an affordable

reliable and maintainable engine next

the engine air Inlet needed to take

shape here things get particularly

unique to the F-117 radar bouncing

around inside an engine Inlet is like a

person shouting into a massive cave the

engine Inlet would need to take the same

facet angles as the rest of the plane

and so the engine Inlet was covered with

a radar reflecting grid the grid had

spacing of just 1.5 CM this spacing was

key to preventing the transmission of

radar the passage of any wavelength

larger than the gaps in the mesh would

be impeded some wavelengths will still

get through but the inside of the inlet

was also lined with radar absorbing

material or Ram which covered the entire

surface of the aircraft we don't

typically see covers on engine inlets

for several incredibly important reasons

number one it reduces pressure recovery

pressure recovery is the ratio of the

average total pressure at the exit of

the inlet to the total average pressure

in the freest stream air the absolute

maximum value is one where no pressure

is lost and therefore no energy is lost

this is a way to assess the performance

of the engine Inlet having a mesh

blocking a large portion of the inlet

drastically reduces es the pressure

recovery and reduces the thrust the

engine can produce as a result secondary

intake doors located here could open at

lower power settings to increase airf

flow but opening these up during flight

was not an option they were controlled

automatically programmed to open when

the plane speed was below Mach 0.5 and

the doors closed gradually as the plane

accelerated this was also how the crew

accessed the engine to maintain it since

the front intake was completely covered

this grid created another much larger

problem during flight ice can build up

on the aircraft smaller devices like the

airspeed pedot tubes have heating

elements and water drains inside them to

prevent this critical sensor from being

blocked to prevent this from happening

to the inlet grid the plane came with

inflight anti-icing equipment with what

was essentially a windscreen wiper a

wiper would emerge from the lip below

the inlet and spray a glycol-based

anti-icing mixture next the engine

Outlet had to be molded into shape and

once again the f-17 has an incredibly

unique design the engineers wanted to

minimize the heat signature of the plane

as well as the radar signature to do

this they needed to cool the exhaust and

distribute it over a wider area so it

could mix with ambient temperature air

quicker the exhaust Outlet transitioned

from a round duct at the turbine exhaust

to a flat 17 to1 rectangular-shaped duct

the duct was also divided it

horizontally into smaller ducted

channels below the exhaust the fuselage

extended out with a slight upwards angle

into what was dubbed the Platypus tail

this shape spreads the heat from the

exhaust over a larger area allowing it

to mix with ambient air and cool down

faster the extension was also covered in

heat absorbing ceramic tiles that were

cooled continually by bypass air coming

from around the engines this exhaust

setup did however cause some instability

issues that were only discovered Ed

during the half blue demonstration test

flights the thrust of these engine

nozzles were angled inwards towards the

center line of the aircraft however the

angle of this trust Vector was often not

symmetric the thrust angle between each

exhaust could differ by as much as 8° in

some flight conditions resulting in

differential thrust that could push the

plane sideways the angle was affected by

engine power angle of attack speed but

in particular Sid slip Sid slip is when

the relative wind striking the plane

does not match the direction of travel

which can often happen on takeoff and

landings with a sidewind this became a

problem for the half blue test flights

because the flight computer was using a

lateral accelerometer to measure Sid

slip but this asymmetric thrust was

pushing the plane sideways causing the

accelerometer to detect side slip the

flight computer then tried to correct

four Sid slip which did not actually

exist and created actual Sid slip which

increased the asymmetric thrust which

increased the false Sid slip signal a

positive feedback loop of instability

this problem was fixed by taking actual

Sid slip measurements using a beta vein

beta is just the Aeronautical

Engineering term for Sid slip with the

engine selected and payload capacity

determined the wings needed to be sized

and designed an aerodynamicist has a lot

of things to consider when designing a

wing The Sweep angle the AO foil design

the dihedral angle and the wing area

usually these decisions are made based

on the plane's main responsibilities an

airliner selects a wing that operates

most efficiently at its expected Cruise

altitude and speed a fighter plane like

the F-16 will be designed to maximize

maneuverability and high angle of attack

lift however the F-117 Engineers had

their hands tied with many of the

choices they could typically make the

sweep angle which describes the

backwards angling of wings was largely

out of their control sweep angle is

usually determined by the speed of the

aircraft slower civilian aircraft like

Cessnas have no need for sweep as they

don't travel even remotely close to

supersonic speeds an airliner Wing is

angled backwards to increase critical

mock number this is the speed at which

supersonic flow begins to appear over

the wings angling the wings backwards

allows airliners to fly faster before

this becomes an issue the 787 has a

sweep angle of

32° supersonic planes like jet fighters

have their sweep angle determined by

speed too but this time it's to avoid

the oblique shock waves emanating from

the nose and body of the plane from

intersecting with their wings which

would cause a large amount of drag and

loss of lift an F-16 has a sweep angle

of 40° even the fastest planes like the

SR71 had a sweep angle of just

53° the half blue demonstrator aircraft

had a sweep angle of 72.5 De and the f17

was going to be a subsonic plane flying

at similar speeds to an airliner a sweep

of 32° or so would have sufficed this

extreme sweep angle was being driven by

its stealth requirements determined by

the echo1 program and this came with

Troublesome consequences a swept Wing

produces less lift than an equivalent on

swept Wing this was made even worse by

the rigid design requirements of stealth

on the AER foil itself the air foil of

the F-117 was composed OS of simple flat

faceted shapes two three on top and two

on the bottom if we map the pressure

distribution of a regular air foil it

may look something like this while the

faceted shape looks like this with Peaks

occurring at the facet lines this

resulted in low lift to drag ratios and

caused issues with aerodynamic flutter

where the wing would vibrate and damage

itself with the reduced lift caused by

the sweep angle in addition to these

suboptimal aerrow foils the wings had to

be quite large to produce enough lift

the designers increased the wing area

with extensions here this increased the

f-117's wing area to 72 M squared a

massive area for such a light plane the

f-17 had a Max takeoff weight of

23,800 kg compare that to an F15 the

F-15 was designed with a low-wing

loading in mind meaning a low ratio of

weight to Wing area and yet the F-15 had

a smaller Wing area area and a higher

Max takeoff weight than the

F-117 the F-15 could simply produce more

lift with less Wing area designing a

plane around these flat faceted sheets

was a huge challenge not just in lift

but in stability too the massive 72.5 de

sweep in the have blue demonstrator

caused a pitch instability if the plane

pitched to an angle of attack greater

than 17° the plane would not be able to

pitch down again as the elevant also

lost control Authority as the angle of

attack increased a concerning pitch

instability that required the flight

control computer to intervene on the

Pilot's behalf with a specialized

control surface the have blue turned the

Platypus tail extension into a flight

control surface it automatically

deflected downwards when an angle of

attack of 13° was exceeded but this too

brought with it some unforeseen issues

which ended the test flight career of

Bill Parks when the control surface

automatically deployed just 1 M Off The

Runway and slammed the aircraft into the

ground bending the landing gear and

forcing the pilot to eject this platypus

tail was removed for the final f117

design the F-117 was different from have

blue in several ways besides being much

larger the inward CED all movable fins

of the hav blue was switched to a vtail

and the fins themselves were enlarged to

increase Control Authority these inward

CED fins matched the the 30° Contours of

the fuselage they served as both the

rudder and elevators a ruter Vader

inward fins like those of the SR71 and

outward candid fins like those of the

F35 work in the same way and we can see

how by examining the resultant Force

generated when the control surfaces are

actuated to different positions we can

actuate them in opposite directions to

generate a horizontal resultant Force

providing yaw control as a vertical

Rudder W or we can deflect them in the

same direction to provide pitch control

as the horizontal elevator would however

the inward caned fins of the half blue

were being shielded from Air Flow by the

fuselage during high angle of attack

Maneuvers reducing their power to

control the plane as they were receiving

less air to create lift the larger

outward CED fins of the F-117 helped

increase the Control Authority the

Platypus tail was removed but the f-17

gained a second outboard elevant where

the have blue had just one elevant on

each Wing these huge full span elevons

were sized to provide more control in

Pitch the 72.5 de Wing sweep was also

reduced to 67.5 de while still an

extremely high Wing sweep for a subsonic

plane this 5 degree decrease helped

increase the lift of the wing and reduce

the pitch instabilities the half blue

demonstrator experienced with two large

elevant the f-117's Vil no longer had to

control both pitch and and yaw it was

dedicated to just yaw control having a

control surface like this performing

double duty can cause issues if the

plane needs to control both pitch and

yaw at the same time the flight computer

has to figure out how to manage the

competing control inputs into a single

controlled surface it's far from ideal

it also increases redundancy in the

event of a failure a much better design

than the half blue demonstrator both of

which were destroyed in crashes with the

extremely poor lift to drag ratio of the

f117 its maximum takeoff weight was

limited fuel tanks were located above

and behind the main weapons Bay with

additional storage in the wings for a

total fuel capacity of 8.2 metric tons

of jp8 fuel giving the plane a range of

1,720 KM to reach enemy territory the

plane needed frequent aerial refueling

the original trip from Langley Air Force

Base to Saudi Arabia for Operation

Desert Storm took 15 hours and required

seven refuelings along the way

air-to-air refueling receptacles were

mounted in the upper fuselage and

rotated into position with the plane's

poor low-speed flight characteristics it

stood a little chance of taking off and

landing on aircraft carriers Loy did in

fact propose a carrier version of the

Nighthawk the F-117 n which added a tail

hook lowered the wing sweep added an

allm moving horizontal stabilizer

increased power with a larger after

burning engine Eng and increased payload

capacity with more hard points The

Proposal was rejected however the F-117

was a moment of inspired Brilliance that

the United States Air Force ultimately

knew would have a limited shelf life

they kept it under wraps for as long as

possible to maintain its Advantage but

once its adversaries knew of its

existence counter strategies began to be

developed taking the simple template of

stealth and trying to adapt it for the

next generation of multi-roll Fighters

was never going to work the worst of

Both Worlds ultimately an entirely new

generation of aircraft were needed

during Desert Storm the Air Force based

36 f-117's in Saudi Arabia and they only

needed refueling tankers as support

these planes operated over heavily

contested airspace with impunity on the

first night of their deployment they

struck 26 high value targets many of

which included the country's surfac to-

a missile defense systems the f-117's

were so effective that the Iraqi air

defense system was powerless to stop

them what was once a Soviet trump card

was rendered useless not a single F-117

was lost this infographic was produced

by the Air Force after Desert Storm to

illustrate the value of this new

technology estimating the 20-year cost

of procurement and operation of this

precision and stealth Doctrine at $1.5

billion the stand standard package of

aircraft needed before stealth was

developed was much more costly requiring

specialized bombers fighter escorts to

protect them electronic jamming aircraft

to suppress air defenses and a much

larger Fleet of refueling tankers to

support all of them costing $6.5

billion however the Air Force was well

aware this golden period of stealth was

going to be shortlived with its

existence known it was only a matter of

time until the enemy developed strategy

and Technologies to counter stealth a

large part of the f-117's mission

planning revolved around knowing the

positions and types of radar systems in

enemy airspace and planning a route

through them that kept the plane out of

range the first and only f117 was shot

down over Serbia in 1999 here a tactic

was used that involved moving radar and

missile launchers regularly and only

turning them on for a short period of

time so their positions could not be

tracked making it impossible to plan a

route around them this tactic allowed

them to successfully lock onto the F-117

and destroy it the pilot was rescued but

the military made no attempt to destroy

the plane wreckage at this point the

F-22 had already made its first flight

developed with the very latest in

stealth technology while being a true

fighter aircraft capable of Defending

itself and incorporating even more

advanced technology that the public are

likely still not aware of today the F-35

employs an entirely new doctrine of

interconnected Battlefield information a

hive mind of stealth aircraft swapping

information between each other the F-117

was the first true stealth aircraft but

as stealth technology has advanced

stealth is not something expected as a

specialization but is expected as

standard with modern technology targets

can be hit from mindboggling ranges the

key to survival is to strike before you

are seen the B2 Spirit was the next

wrong on this evolutionary ladder and it

was one of the most sophisticated and

expensive planes ever produced we don't

have a video on the B2 Spirit but our

friends over at mustard do and it's

available exclusively on nebula the

20-minute video is beautifully animated

and tells the story of how the B2 came

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