Scud Running: Should You Do It?

Pilots · 8 min read · Oct 04, 2022
Scud running

In the world of aviation, there is a vast terminology for the many different aspects that are involved in flying. There is a wide variety of maneuvers pilots perform in the skies to sort different situations and make sure they reach the destination airport. Among them, there is one called scud running.

There has been a lot of debate on whether scud running should be taught or discouraged, whether it should be deemed illegal or not, among other things.

So, if you want to discover the most relevant information about scud running, we invite you to keep reading as we disclosed the details.

Two Desert Air airplanes scud running over the Namibian Desert.

What is scud running?

We can say that scud running refers to the practice of flying at a lower-than-usual level to stay beneath clouds and avoid instrument meteorological conditions (IMC). During scud running, the pilot should decrease the height to remain below inclement weather and maintain visual flight rules (VFR) instead of the instrument flight rules (IFR).

Another definition is provided by the Federal Aviation Administration (FAA) which describes scud running by stating “pushing the capabilities of the pilot and the aircraft to the limits by trying to maintain visual contact with the terrain while trying to avoid physical contact with it.”

Why is it called scud running?

According to the National Weather Service in the United States, scuds are “small, ragged, low cloud fragments that are unattached to a larger cloud base and often seen with and behind cold fronts and thunderstorm gust fronts.” Therefore, the term scud running is used to define a maneuver used by pilots when they encounter scuds.

Scud clouds.
Image source: (CC) Rollcloud/Wikimedia

Why do pilots do scud running?

Scud running can be considered dangerous but pilots continue to do it, despite the risks. Occasionally pilots decide that scud running is justified because it is necessary for their specific situation. Occasionally, the pilot will be running with scuds due to an error that affects his aeronautical decision-making. The most common, yet often times mistaken, reasons to engage in scud running are the following.

  • Following a planned course of action mindset. Many pilots feel forced to continue to their destination and complete their flight even when there are low clouds and bad weather conditions.
  • Taking the “macho attitude”, one of the 5 hazardous attitudes any pilot should avoid.
  • Believing they can continue with a controlled flight because they know the flight path very well.

Yet, no matter the reason, scud running has proven to be a very dangerous practice.

Why is scud running dangerous?

According to NTSB and FAA statistics, continued VFR flight within the IMC has become a leading contributor to general aviation accidents. And these accidents are usually fatal.

In scud running, you will take dangerous flights near the ground and push the limits of your abilities, and the limits of the aircraft. Because of the nature of scud running, it is easy to understand why it is associated with controlled flight into terrain (CFIT) accidents which account for 17 percent of general aviation fatalities.

Scud running is dangerous because continued VFR flight into IMC also often leads to a CFIT accident. Controlled flight into terrain is a very real possibility with scud running due to a combination of multiple factors.

Let’s take a look at a couple of these factors.

Maintain visual contact with the ground and landmarks is difficult

Legend motion picture pilot Frank Tallman once described how pilots are lured into believing that scud running help them maintain visual contact with the ground and landmarks, thus having a safer flight path.

Tallman said “When a pilot is scud running in gradually worsening conditions, he might glance rearward to appraise his escape option. But when looking aft, the pilot observes the landmarks disappearing into the veil of limited visibility behind the aircraft.

This creates an illusion that can lead him to believe that conditions behind are worsening or closing up. Contributing to this deception is the illusion that conditions ahead are improving. This is because the airplane’s forward motion allows progressively more of the landmarks ahead to come into view.”

However, it is well known that worsening conditions will reduce forward visibility, making it more difficult to identify those landmarks coming into view. Moreover, the reduced visibility will force the pilot to fly at a rather abnormal low altitude, making the scud running pilot take the risk of encountering buildings and other type of constructions, as well as topographic landmarks in the flying path. This increases the possibility of scud running accidents.

Low altitude flying reduces reaction times

Even for the most experienced pilot, flying low highly increases the possibility of making a mistake. In this situation, the distance to the ground and to any obstacle like cell phone towers or similar constructions is very short, so a faster reaction is required in case of emergency. Add the reduced forward visibility and you get a combination that spells disaster because the pilot’s reaction time may not be enough.

This gets worse when flying at higher speeds, something that is common in a scud run because the pilot is trying to get out of the situation as quickly as possible. As described by the Aircraft Owners and Pilots Association, “When flying at 180 knots, for example, it takes only 20 seconds to cover one mile, which might be the limit of forward visibility. Precious little time is available to see and avoid obstacles.”

A small aircraft scud running over a church tower.

How can scud running be avoided?

While pilots have been forced to perform a scud run in very specific harsh conditions that left almost no alternative such as navigation equipment failures, strong headwinds at IFR altitudes, ice or turbulence, scud running and the dangers that come with it should be avoided.

Avoiding a scud run can be so critical for safety that the aviation division of Transport Canada used a sort of questionnaire to discourage their pilots from scud run. The questionnaire required pilots to consider the following questions before engaging in scud running.

  • How much airspeed is lost when a pilot rapidly rolls into and holds a 45-degree banked turn?
  • How much room is needed to make a 180-degree turn?
  • How much additional space is required if turning from the upwind side of a valley to the downwind side?
  • How far away can a pilot see a wire (power lines)?
  • How much distance is flown from the time a pilot first sees a wire strung across his flight path until he can react and begin a climb?
  • How prepared is a pilot to cope with a fuel tank running dry or having an engine fail at very low altitude?
  • Can your windshield withstand hitting a two-pound bird?
  • Do you still feel like flying at low altitude in limited visibility?

As we can see, the questions above lead to pilot to identifying the dangers of performing a scud run.

Scud running pilot alternatives

In general, scud running takes place because of poor weather conditions. Therefore, the most obvious alternative for a pilot is to stay on the ground and wait for weather conditions to improve before taking off. However, weather conditions can change in the middle of the flight. So, what are the alternative then?

Well, another alternative to scud running is also found on the ground. Becoming an instrument rated pilot and becoming proficient at Instrument Flight Rules (IFR) flight can make a big difference when weather conditions suddenly change.

When the pilot is in the middle of the flight and the weather worsens under Visual Flight Rules (VFR), the pilot may consider the prospect of a dangerous scud running scenario, or remember the aeronautical decision-making process. The best choice will always be to weigh the options and systematically select the best course of action given the circumstances.

First of all, by being IFR-rated and having a properly equipped aircraft, the pilot can request pop-up IFR clearance. This type of clearance is used to switch from VFR flight into IFR without the need for a previously filed IFR flight plan. The ability to request a pop-up clearance can help pilots get out of a worsening situation. In this case, the pilot must keep in mind that the controller will confirm whether it is possible to maintain terrain and obstruction clearance until reaching the minimum instrument altitude (MIA).

Another alternative for the pilot is to consider different destinations that may be reached with the current available fuel. Whenever another destination exists within range, diverting may be the safest alternative, especially when it allows the pilot to avoid the worsening weather.

Also, the pilot may be able to make a safe 180-degree turn and retrace the flight path back to the departure airport to wait out the weather. Even when having limited visibility, taking the turn and finding guidance lines like river valleys or roads can make up a better alternative than continuing with a scud running flight.

Finally, the pilot may be flying over a remote area with no alternate airports, and turning around may not be an option. Lets assume that the pilot in this situation is not IFR rated either, or the pilot is flying a non-IFR-capable aircraft. In that case, it may be time to consider emergency landing areas as the safest choice.

A small aircraft flying under marginal conditions for VFR.

Closing remarks

Despite the dangers we have described above, scud runners still exist. And they will probably continue doing so for years. Now, remember that when you fly low, excessive speed may increase the dangers to crash into radio towers or other obstacles. Also, just because other pilots are doing it, it does not mean that you should too.

Flying at low altitudes can have some benefits like better views, avoiding rough weather, and even taking advantage of the wind to build up fuel reserve. However, flying at a lower altitude must be done under controlled conditions and with the knowledge of the risks.

In short, the least you fly at low altitudes the better. By complying with the rules, you increase your safety and the safety of others that may be affected by an accident that could have been avoided.

Scud running FAQs

Now that we have provided all these details, you should have a better idea about scud running, what it involves, and whether it is recommended or not. However, just in case you are still wondering if there are more specific details, we leave you some of the most common questions people ask regarding the topic of scud running.

Is scud running legal?

If you are given a standard attorney answer: It depends. Most days, scuds are legally allowed to be performed. However, certain requirements exist.

Depending on the airspace, the visibility required may vary. Commonly, the requirement falls between one and five miles visibility.

Also, based on the airspace, required clearance can either be as simple as “clear from clouds”, or the measured distances of 500 feet below and 1,000 feet horizontal may apply. In any case, the pilot must fly above as high as to have a successful forced landing in the event of an engine failure. With this in mind, scud running usually has a legal status. However, performing legal scud runs can be challenging in congestion. For example, if you are 300 feet above an interstate the fact that you are flying over cars makes the operation illegal.

The visibility required depends on the area where you fly. As we said, depending on the airspace required clearance can simply be cleared of clouds, or measurements at a distance up to 1000 feet may be necessary.

Can student pilots fly marginal VFR?

Student pilots cannot take solo marginal VFR flying. Of course, this is an important part of the student pilots training, but they must go through this type of situations with a certified pilot instructor.

What is a “duck under” in aviation?

“Ducking under” in aviation refers to flying low, below the published minimum altitude to sort certain conditions like low visibility that do not allow the pilot to see the runway.

However, this is normally not the best course of action, which is why the “ducking-under syndrome” must be avoided. While experiencing the ducking-under syndrome, a pilot may be tempted to make it into an airport by descending below published minimum altitude during an approach.

The pilot may believe that there is a built-in margin of error in every approach procedure, or the pilot may not want to admit that the landing cannot be completed and a missed approach must be initiated. Therefore, these kinds of decisions usually end up badly, and many accidents are associated with this syndrome.

The fact that it refers to flying below published minimum altitudes is the reason why it is associated with scud running.

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Jet pilot @NASA

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